Hi,
2009 CTSV, 2.45 upper pulley, ported snout, injectors, 90mm TB, cai, very mild LT1Z 1.0 cam. Engine starts fine, idles fine, WOT fine. Issue is that at normal acceleration from a stop, and / or at a shift point, the engine stutter and sputter for 1-2 seconds like small and sometimes larger backfires . The log shows boost will jump sometime up to 8 or more pounds, but the throttle is steady and low (like a backfire is causing the intake pressure rather than throttle / supercharger). I have not been able to figure this out.
Normally at WOT I get little to no knock, may a degree or two but not much. When it spits and sputters just off idle or at the first or second shift, there usually isn't a lot of knock associated but the first event I captured at 13.00.19 was significant.
Any ideas?
See attached log ... great example is at time marker 13.00.19, and another at marker 13.01.46.