ninobrn99

iTrader: (8)

When i start the car cold, it starts up fine. it smells like fuel really bad though. lets say i pull out of my parking spot and its still cold. ill reverse and then put it in first gear and start to go. when i let off, the idle drops to about 1500 and stays there. as it warms up it gets lower and lower until it reaches where it should be, about 950. well i take off and drive for a few seconds. when i let out the clutch, take it out of gear and brake, the rpms dip down to about 250-300 and then climb back up again. it does that for a bit, then will finally stablize after a while. however, when i try to give it more than 60% throttle and shift quickly, i can hear it popping in the exhaust. any thoughts as to what could cause this? it happened after i dyno'd it and has been doing it since. now for the mods:
370 iron block
stock ls6 heads
prc springs
f13 112
pacesetters
tsp catted y
ram clutch
42# injectors
royal purple 10w-30
ngk tr6s
msd 8.5mm wires
ls2 chain
stock oil pump
stock alt.
stock water pump
ls6 intake
stock ported tb
maf in place, but running in sd
o2s are enabled
MTI lid
asp pulley
ive also noticed that there are a few times that im going to turn from a stop and the car sputters and seems like its going to die, but still goes, but barely! no matter how much gas i give it. its happening a bit more often than it did in the past. im thinking maybe its the pulley, but havent had a chance to swap them out to see.

ninobrn99

iTrader: (8)

also, ive had my battery and alternator checked and they're both fine. i havent pulled my plugs to check them yet, but ive thought of doing the following:
changing my plugs
wires
intake gaskets
iac sensor
tps sensor
crank pulley
and also the oil. going back to regular oil. i did notice it started happening after the last oil change. not immediately after, but after it.

97BlackLT1TA

iTrader: (4)

It sounds like a tuning issue to me. Did you have it tuned when installed?

ninobrn99

iTrader: (8)

yes, i had it tuned. it ran fine. the only time i had a similar issue was when the maf was plugged in. when it was in speed density, it didnt do it. i dyno'd it with the maf plugged in and thats when it started happening, even in SD.

lsx24

iTrader: (45)

You need to get some logging done. Get to the dyno or do it on the street but get samples with HPTuners or EFI Live or something to make sure your tune is not off, and all the parameters are within spec. Or if you don't know what specs to look for talk to your tuner to make an appointment for him to do that. At least this will give you an idea of what your car is doing from an electrical standpoint.

I'm assuming you checked the obvious things being vacuum leaks (any hoses disconnected from the intake), tb sticking action, bad gas, etc...