Thread: Bought a 05 GTP, have some questions

Hey guys I just bought a 05 GTP a month or so ago as my first car that I got with my own money, and I absolutely love it. I have been looking around to try to find the answers to some of my questions, but I have a quite a few that I would love to get answered. Some may be stupid but bear with me Also, just a few pictures of my new ride Grand Prix - Imgur.
1. I got this car from a dealer who got it from an auction and one of the previous owners did a few mods, but it got repoed from him so I am not 100% sure of all the mods, but from what I can see it has a k&n cold air intake, slp exhaust (all the way up to the headers), and probably a reprogrammed pcm (this is a guess based off the fact that the owner probably wouldnt put all the other money without also reprogramming it, and also it has pretty high mpg [22 city 30+ highway]). According to some research on these mods i would be getting about 35? extra hp (20 from cold air and 10-15 from exhaust). Is this sound about right, me getting 300 hp and 300+ ftlbs torque?
2. How would I go about testing if the pcm is in fact reprogrammed?
3. Even though this is just a daily and the manual says it can run 87, I should run premium(93 where I live) in this right?
4. Could someone explain to me about the grounding problem found in the aftermarket radios? i found one post on it but it wasnt too informative, and I think I have that problem.
5. Would you recommend the use of synthetic oil?
6. I am in desperate need of new tires, so is there a specific all season tire you would recommend? (I live in MI so i have to deal with snow, ice, and rain frequently)
7. What is the best technique to get the best jump? just jam on the gas or hold the brake and rev up the rpms first or????
8. I have cloth seats, and I want to put in the leather as i think they look amazing, would I be able to just drop in some from say a 06 gt or do they not fit that easily?
9. Has anyone painted their calipers? was it a hard process?
10. My low note on my horn is out, and I was wondering if it was a difficult job to put in a new one
11. Have you put in the led interior lights? do they really make a big difference? was it hard?
12. Are there any other inexpensive mods that are really nice? (the leds for ex.)
13. I have read that gtps has the power of a v8 with the mpg of a v6, is this true?
Sorry I know there are alot of questions, but i really appreciate it if you all could help me out!
Once again just saying that I love this car, it is honestly amazing. This is also coming from a guy that was driving a pt cruiser for all of high school (I'm 20 now), its a huge improvement
Thanks in advance!

1. Where have you been searching that says the cold air intake adds 20 hp and the exhaust adds 15? Those 2 mods at the max might give you 5 more hp.
2. Most aftermarket pcms will kick the fans on at 185ish instead of the stock 213* and they also keep the fans on after the car is shut off, that is the easiest way I can think of.
3. I wouldn't run anything less than 91, especially if you are unsure of what mods have been done to the car.
4. Do you have any humming or any weird noises in the sound system?
5. You can use whatever oil you want. There is a few threads talking about oil search and read them.
6. Firestone or Bridgestones. Stay away from Goodyears.
7. Don't jam on the gas, practice easing into the gas then going wot till you get a feel for what works best for you.
8. Yes as long as they are out of a 04+ gp they will bolt right in.
9. Again search the forums or google or youtube tons of info on doing this.
10. Probably not should probably take less than 30 min
11. I haven't no, but from what everyone else that has done it says they make a world of difference, and it looks pretty easy to do.
12. These are a lot of inexpensive mods that can be done search the forums, look at others rides, read stickies, there is one for mods that cost less than $50.

Don't believe the b/s HP claims that vendors try to feed you. True is most are full of s**t. It's a marketing strategy to get the customer to purchase it. Thankfully you bought the car with it so you didn't waste your money on it.


Getting 300whp isn't exactly is it takes a lot more mods like a intercooler and cam to pull that off.

Plus our trannies are already week. Added power just adds stress.

Exhaust is just a waste for the price you pay. The stock exhaust isn't restrictive until around 300whp then it needs to be upgraded most will never reach that point. So basically your doing it for a different tone which can be achieve much cheaper by cutting off your stock mufflers and welding whatever mufflers that you want.


Read this

http://www.grandprixforums.net/safel...0-a-67580.html

Originally Posted by slick2500

1. Where have you been searching that says the cold air intake adds 20 hp and the exhaust adds 15? Those 2 mods at the max might give you 5 more hp.

Well don't forget he did mention headers, not just a cat back. So that's more than 5 combined.

9. I have painted calipers on my car. It's not hard, but time consuming depending on how good of a job you want to do. Since you only see the outer and top part, some people leave them on the car (on the knuckle) and just tape everything off, prep and paint. I removed all 4 calipers, and brackets and scraped, wire brushed, and cleaned with brake cleaner before applying 4-6 coats. It's holding up great so far. My only regret is that I didn't get 100% of the old paint off first, some was on there good so I left it, I should have used an angle die grinder and a scotch brite pad on it. (if you remove all calipers, it's a good time to do a brake fluid flush)

12. http://www.grandprixforums.net/ultim...0-a-49055.html
^ This is a decent list, there are many that should have been added to it but I'm not sure if the user is still active or not. The posts below suggest more things. (Let me say trying to find that post was absolutely impossible using the forum search. I spent 5 minutes and couldn't find it. I typed the same stuff into google and bam the first link there it was.)
http://www.grandprixforums.net/safel...0-a-67580.html


13. This is only true in the case of a bit of modding due to be being supercharged. At the time, the 3.8 SC made about as much as a small V8 of its time in 98-05.

Also since you just got it, maintenance is a great place to start, that can give a bit more HP and better mileage.

Yeah it took me two days to completely paint the calipers. From when the car was used to the time I was able to use it again. Just make sure you get them to bare metal and use brake cleaner to get 100% of the dust and grease off.

If it's got headers, check what pulley is has on the supercharger. Sometimes people unsafely mod the 3.8 and you wouldn't want to have excessive kr.

I've got the N/A 3.8, It had plenty of power for me at first, but I'm now realizing the high end power is kind of lacking. It's plenty fast off the line though. I'm sure the S/C 3.8's are just fine at higher rpms, especially with headers. Who knows, maybe that will be my next car, I love my Grand Prix in every other way so far.