Strange noise...??
https://ls1tech.com/forums/generation-iii-internal-engine/501422-please-explain-spark-knock-rattling-can-noise.html
Its a part throttle, only when engine is warmed up, type of noise.
In any case, please update me when you get the headers/ypipe/cats on...I'd also like to rule out the cats if that fixes your problem.
I'm running SLP LT's with thier high flow cats.
What LT and cats are you going with?

