Join Date: Apr 2003
Location: Terre Haute, IN
I'm no 930 plumbing expert. BUT bucking under loads at certain rpms makes me concerned of AFR's. Rev's in neutral are more transcient and more forgiving without load. Cold start settings are purposely running at richer AFR's and therefore might cloak a lean condition. When under "full acceleration" your under most load and typically more boost. These are both going to be conditions most sensitive to AFR's.
You upgraded/restored a lot and though we often question parts failures, could it be more likely simply adjustments out of range?
I would think a vacuum leak would effect idle. Vacuum leak symptoms get better under full throttle. I agree that a pipe/hose leaking would likely be more broad in areas of effect.
I say, get hold of a broad band O2 or dyno. If your brave, adjust the CO2 to the richer side in this rpm range and see if hesitation improves?
If a cylinder was leaking this bad I think you'd see other symptoms. That plug might show issues. You could check compression. I think you could determine by selectively checking by eliminating clyinders. I would think that it might be worse when cold as tolerance usually work in your favor as she warms up.
How long has it been assembled? Has this issue came about out of blue or after changes? What is your skill level and how hands on are you?
Merry Christmas, All!
72 RS spirit 2.7mfi, 73 3.2 Hotrod on steelies, 76 993 3.3efi TT, 86 trackrat, 91 C4s widebody,02 OLA winning 6GT2, 07 997TT, 70 914 v8