Random popping. Help! (long)

[SyHopeful]

So for a while now I've had an on-and-off problem with my GN. This problem is a random popping or chuffing noise coming from somewhere under the hood during medium to high acceleration.

Symptoms: It usually happens around 13-15psi and the car acts like it's all-of-a-sudden venting it's pressure before it gets into the engine, like having a boost leak that only appears around 13-15psi. It hesitates/lurches a bit, I hear a hollow "POP POP POP" from under the hood (or maybe more like CHUFFCHUFFCHUFF), my boost gauge dances around a bit but never indicates any overboosting, and my knock gauge (tied into factory knock sensor) will instantly read anywhere from 3-7 degrees of KR, but I don't believe it's seeing actual detonation. I always let off, and I have yet to find any obvious cause. Oil is clean, doesn't blow any smoke at all, all hoses and lines appear to be tight and secure.

The possible causes I've thought of:

Boost leak:
The car acts like it has a boost leak when this happens, however I figure if it was a boost leak it would happen every time I get around 13-15psi. Yesterday I did 4 high-speed pulls with the pedal buried and blowing 15psi with no knock and no popping. Today coming home from work I tried to to get on it and I got the popping.

Bad battery/alt:
My lights dim pretty noticably when I use the power windows or locks. My headlights also sometimes flicker when I'm driving around normally. My battery is at least 2 years old and has been through one harsh winter (2003). Could that lead to some sort of ignition problem?

I've tried to find some condition that is always present when this popping occurs, but no luck. Ambient temps make no difference, how long the car has been running immediately prior makes no difference, I fill up from the same gas station, etc.

I need to go do a few runs with T-Link, but I figure this kind of problem would be a bit more obvious.

Sorry for the long post. Any ideas? Much appreciated!

EDIT for my mods:
009s
Accufab billet FPR (Set to 42psi line off)
Eric Marshall chip
SMC alky
PTE FMIC
Walbro 340 + hotwire
Casper's TPS-tec
Exhaust cutout
Hooker catback
K&N cone filter

Everything else is stock.

 

[pwr.slave6]

Sounds like its starving for fuel under boost conditions.
Do you have a fuel pressure guage? check if fuel is droping off
when the condition occurs.

 

[my85grandnation]

I had a similar problem where mine would surge under power then pop just a bit. It turned out I had my spark plugs gapped wrong. They need to be gapped at .035, but most places like chiltons books and other places list that our plugs need to be gapped at .060 this will work for a while then it starts to wear out your coils so they wont jump that far of a gap.

 

[SyHopeful]

Sounds like its starving for fuel under boost conditions.
Do you have a fuel pressure guage? check if fuel is droping off
when the condition occurs.

I do have one, and it's been a while since I've checked for drop-off. I'll check it out when I get up!

I had a similar problem where mine would surge under power then pop just a bit. It turned out I had my spark plugs gapped wrong. They need to be gapped at .035, but most places like chiltons books and other places list that our plugs need to be gapped at .060 this will work for a while then it starts to wear out your coils so they wont jump that far of a gap.

Well I replaced the plugs and wires barely 2 months ago and took extra care to make sure they were gapped at .035". AC Delco CR43TS plugs and MSD 8.5mm Supers.

 

[TurboDave]

I think the answer is far simpler! Solution simple? no, but an easy diagnosis. What it sounds like you're describing is a case of compressor surge. Most common when a front mount I/C is added to the system. Sometimes it takes some modifications to the inlet tract (volume), or in many cases it can be solved by an aftermarket boost controller that has a fast turn on/off, as apposed to the stock chip's signal which is a very slow (2.5 seconds) ramp.