Dynoed today...sucks...:-(

Your problem sounds a little like mine, except at a much lower rpm. Mine doesnt get bad til after 6000rpm.
How does it drive on the road ? Will it go beyond 5500rpm ?
But the problem is still there..Not as bad though..Going to recheck the wires while there hot...edit...all the wires check good hot..I will probably buy another set just to try it... Runs real strong to 5500rpm then feels like a miss but keeps pulling.. Replaced the idler and there is still a bad squeak. Sounds like maybe the water pump... Squeaking from somewhere around there...
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Haven't ohmed my wires yet, that's next on the list.......
So if you have the boost turned up then turn it down a lil.
went for a test drive tonight, about 10 mins into it the squeak got real bad, then the belt broke
.. Luckily I was able to make it home..Jacked it up and spun all the pulleys by hand, the sprung tensioner I couldn't spin at all and the idler/manual tensioner on the head unit is real rough when you spin it..Wonder if the tensioner was sticking at high speed causing the sputter/surging...Damn, gotta pull the steering rack to replace it too 
Chris



I just ordered a set..Oh well, thanks though...I will let you know how it goes...