Dude, thats the EXACT same thing that is happening to my Radix'd SS. I thought it was my torque converter locking (which it was doing also) but when I hooked up my scangauge, it would show over 6-7.9 of Knock Retard and drop my timing from 12-14 down to below 8degrees of timing... if I were you, I would hook up a scangauge ASAP and check out whats going on. My 1st and 2nd WOT would be fine, but when I get into 3rd gear, it just falls flat.

 

Sounds like fuel pressure issue

 

Didn't see a drop in FP on gauge. Going up on dyno again on the 16th. Will check it out.

 

That would be my assumption as well. Nothing like a serious KR spike to really pull back the power...