I have the HKS SSBOV and am pretty much strait BPU. The turbo's were stuttering when I got off the throttle at midrange boost levels (>.5 bar). I loosened the screw but it still stutters a little at negative boost levels when I get off the throttle. Is this bad for the turbos even at negative boost? How loose should the screw be for a strait up BPU auto? Thanks.