Since I put a Forge BOV on my Evo I've been having this problem. The BOV flutters under any sort of PARTIAL throttle. The worst is on the freeway. If I give the car partial throttle to accellerate through traffic a bit, and the car builds a small amount of boost (1-5psi or so), the car bucks back and forth, building boost and blowing it off/bypassing air continuously.
The other thing that happens is under partial throttle, higher boost, higher rpms (4500+). The BOV seems to flutter. No bucking, just fluttering.
The worst is when both of these are combined (little of each case above going on).
I also have a hallman MBC hooked up. Both the MBC and Forge are fed manifold pressure, but from seperate feed lines.
Anyone have any advice? Here's some cell-phone vids of these conditions:
http://www.scheides.com/misc/MOV00012.3gp
http://www.scheides.com/misc/MOV00016.3gp
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