Boost creep is when boost climbs higher than what you set boost for. You're waste gate is not handling flow and it's taking easier route through exhaust and continually spooling turbo. Causing loss of control of boost. Hopefully you have a aftermarket boost gauge and you're watching it. If it climbs higher than you originally set it for, that's probably boost creep. I used to have a Buschur upgraded denso fp and had to go to a Walbro 255 lph. Buschur's didn't supply enough fuel. This is only with a small ported 16g, fmic, and VPC at 20 psi and 3" catback. I'm also using 550cc injectors. Pump could have been defective or just ran out of oomph. I believe my denso only flowed like 165 lph. As far as I know all mbc's fluctuate a bit. Most of the low end electronic boost controls do the same but you can adjust it from the cockpit instead of under the hood. The HKS EVC IV has fuzzy logic which will control fluctuation.