p0171 help

[Timing]

Hi im new here but ive been reading all the posts for awhile here since i got my vehicle. (2000 pontiac grand prix 3.8 sc) First things first i was initially getting evap code so i changed my gas cap and had my light turned off. I also replaced my air fliter. shortly after my light came back on. But then it would turn off and then back on again. I did have it blink a few times one time then shut off. But a couple days later it came on and stayed on so i went to AZ and had it read again and it stated i had the same p0144 code i believe it is and then i had the new p0171. and after reading this forum i knew i was in for it. My initial thought was maf so i took it off and cleaned it up. I also cleaned my egr and pcv while i was at it. And the light is still on ive tried shutting the light off by disconnecting the neg bat cbl for like 10-15 mins but it hasnt shut off so im assuming it can only be shut off with a computer.
Ive recently installed a sound system and hooked up my positive to the easy access spot for the battery but i highly dought this is it bu i have read some stuff about battery connections cousing the code but i dissconnected them cleaned them up(they really wernt dirty) and put them back on nice and tight. I thought also a vacuum leak and i sprayed all along the hoses with carb cleaner but found no difference in idle. I do however hear a small leak sound but my boss( ase mechanic) says he thinks its a exaust leak. I havnt changed my plugs and wires out since ive had the car about 10k miles. I have read alot about this code and want to narrow it down im just kind of unsure were to start. I think i might have a smoke test done to make sure there is no leak. The car has 191k miles but the engine was rebuilt about 50k ago and runs great up till this. Im not having a huge power loss but it does seem like it doesnt have the power it had befor. Im going to change out the plugs wires and fuel filter and see if anything changes. (what do people recommend for these) and after that if no luck im think o2 sensor but befor i dump the money into that is there and easy way to check it. Any input would be greatly apreciated, i really dont have much money im working at a gas station/garage so ya... lol thanks in advance

[Timing]

oh also another thing to note is when i got the car it had been running 87 and since then ive ONLY been running 93-94, also befor the code came on last week i did put in some of that complete restore stuff and filled my tank with 94 and it was running very sluggish but after that tank burned down i filled it again and power came back and thats also when the code came on

[Austins01GP]

start with the plugs and wires i like the autolite copper cores, but many people like the irridiums. And the stock ac delco wires from autozone work just fine dont worry about getting some fancy kind.

[Timing]

Should i just stick with the original plugs since its all stock. Or if i do change them due to miles what brand/core should i go with cus i did see something about bill saying these cars didnt like certain brands like bosch.

Edit: also my chiltons says keep gap at .060 but ive read people saying .050 or.055

[Austins01GP]

bills smart about these cars.. im not an expert but, since your stock i would just run the autolite copper core 606's, they work great in these motors and are like less than 2 dollars a plug IIRC and might aswell pick up new wires because cause you just got the car and if they are probably old

[Timing]

bills smart about these cars.. im not an expert but, since your stock i would just run the autolite copper core 606's, they work great in these motors and are like less than 2 dollars a plug IIRC and might aswell pick up new wires because cause you just got the car and if they are probably old

ok thanks bud ima go grab some when i get paid this week and see how that goes but i still dont know if i shoukld change the gap or not and is there any special fuel filter i should buy

[Austins01GP]

gap to .055 IIRC maybe some one can make sure of that? and i havnt messed with any fuel filters but im sure the stock replacement is fine havnt heard of any "better" ones

[Timing]

ok so i figured ide scan my car just to be sure and i guess when i cleaned the maf egr and pcv it must of shut off the code cus the only thing i got this time was p0442 and another for traction control but i still am only getting like 15-16 mpg and my power is slacking but ill try the plugs wires and filter. what could cause the p0442 besides gas cap? im guessing hole in step or something or evap canister

[BillBoost37]

As mentioned flashing light is typically a tune up.

171.. search on my username and that code. Once you do, you won't be changing the O2. And..if you pulled the battery cable off the battery to put your system in.. pull it again and look for corrosion.