My 2005 LGT is at the shop right now, and they're trying to figure this one out.
Under steady or heavy acceleration, moderate boost I get a pop, pop with power loss, then it works. Often doesn't happen again until next time I drive, but has been getting worse.
Sometimes flashes the CEL for 10 sec, then goes out, sometimes gives a cylinder 4 misfire code w/flashing Cruise light.
Have tried swapping injectors and coil packs, problem stays on cylinder 4.
Compression test ok, smoke test for boost leak ok, fuel/air sensor was destroyed on cylinder 4 (probably from backfire), replaced, swapped up-pipe w/catless, still backfired so swapped back.
Discovered someone put in the wrong plugs, changed.
Still backfires occasionally.
They don't think it's a burnt exhaust valve because compression was ok.
The mechanic mentioned that it's backfiring through the intake.
I've scoured the forums on many sites, any other ideas?