Thread: Downpipe

After months of misfiring and horrible gas mileage I finally decided to address my p0420 and but a new cat. But I noticed for about the same price I can get a downpipe instead. I'm just confused on 2.5 or 3 inch. I emailed zzp and they said 2.5 would be perfect but I've read through a few forums that say otherwise. I have an 04 gp GTP completely stock. I plan to eventually make a cai and purchase a power log.

Also I plan installing the dp myself. It looks like a couple Bolts and a pipe is there anything that may complicate that? And will I need any other parts that don't come with it

I think its a 3" on the gtps, and 2.5" on the gts. I put a 2.5 zzp downpipe on my 01.

There are two bolts where it bolts into the engine, and two under the car where it goes to the resonator. The two that were in the engine came out like butter with my impact gun and the right extensions. The other two had to be drilled out, and I messed the resonator flange up. I ended up getting a whole exhaust off a 2004, for 60$. I put the exhaust on my car, removed the dp from the exhaust and used the ZZP dp.

The 04 exhaust fit perfect, and i don't get a bad smell anymore like a bad cat.

If you heat the bolts up, soak with pb blaster, they may start coming off, but I would replace with new bolts, as those get VERY rusty. I broke both the heads off when I tried putting a breaker bar on them to break them free. I soaked mine for a week, and had a torch to heat the bolts up a good bit.

The DP on the exhaust came off fairly easy. I was able to get the right angle with my impact gun and heat them up, and they both came off, first one came right out, second one started to strip, then it finally came.

get the 3 inch. why upgrade later on? stocks not 3 inch either, on a gtp or a gt.

I see, i thought the gtps had a 3", but i was wrong.

its all the same. why the 3 inch is a up grade, will go well with the plog.

if you need a cat you can get a high flow 3 inch cat for 50 shipped off ebay. likely cheaper then zzp catted dp.

then theres speed daddy, they have 3 inch down pipes as well.

The resonator flange bolts might not break if you can use a torch to heat the flange. In my experience, one will snap off. You can drill that out and use a bolt and nut, no worries. The front ones might back out a stud but thats OK. If you buy a zzp DP, they can come with proper gaskets depending what you order. I have their 2.5" dp on my 99 GTP with no complaints but use a rear 02 emulator. I got mine so I'd have a new flex joint, cat, and u-bend delete all in one. The only thing to swap over is the O2 sensor.

they fit all years, same engine still.

Originally Posted by Teecraige

So this http://m.ebay.com/itm/RACING-HEADER-...984?nav=SEARCH is good?


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no, this one http://www.ebay.com/itm/STAINLESS-SS...FV32nk&vxp=mtr


the one you posted has a extra down pipe included for no reason at all. makes no sense really.