I had the same problem with my car when it was stock!! My boyfriend/ abused mechanic checked over all of the clamps and hoses and tighted up a lower clamp near the intercooler. Problem went away! After the install of the downpipe straight pipe and exhaust, problem came back. one week later I (he) installed the HKS BOV and the problem hasn't returned its been about 3 months now!

 

Beckel - you are dead on point. The cold has everything to do with my 8's "brick wall" . Anytime the weather dips below 40 this happens. It's so violent I almost think the internals are breaking loose.

I'm going to lower the boost from 21 and regap the plugs, may even consider the copper NGKs you mentioned. Would a colder plug help I wonder..

Tonight it actually lit up a CEL. Hopefully a mismatch in 02 signal caused the light to burn.