EFI Tuning Question (Big Blocks, Blowers, Flat Spots at ~3K RPM)

[RSX302]

I have tuned a couple of blown big block chevy's (GM572 w/whipple and a BBC w/Procharger) and both had mild flat spots around 3-3.5k rpm while cruising part throttle. Idle to 3k rpm perfect..mild accel thru 3-3.5K 'bobble/flat spot' and then will smooth back out the rest of the way up. Land on it and it will power right thru without notice. I've tried cuising A/F ratios between 12:1 & 14:1 along with timing from 20-40 degs and tip in fuel +/-. All other drivability and power is great except for the lousy mild bobble/flat spot.

Nothing seems to affect and we are thinking its the big block cams and blower combo? The 572 cam is factory and I'm sure if milder cam was installed, that would help it out? I need to look again at the manifold pressure to see exactly where it starts. 5"hg, 0psi? We are good on the boost side.



One system was a Fast XFI and the other Accel Gen 7.

Any input is greatly appriciated.