My car just started doing this same thing today. As soon as the car reaches 0 vac, it hesitates and sometimes backfires out the intake. I know it is due to fuel being cut because I can see it on my a/f gauge immediately. Every time my car hits 0 vac, my a/f gauge shows waaay lean and acts like it is in open loop mode. I think that the reason for this with my car is because I richened up the 8 injector setup and set it to start squirting fuel at about 1 psi. My guess is that after a few days of driving this way and WOT pulls, the ecu developed a new WOT fuel map for open loop driving. I'm thinking that for some reason, that regardless of the throttle position, the car is going into open loop mode, and the fuel map for it is extremely leaned out due to all the extra fuel that I am adding with the 034EIC at low boost. I am gonna try a few different settings on the EIC and datalog the car tomorrow to try to solve this problem.

For the guy above that was saying that he was getting backfires out the intake, that is a very strong indicator of running too lean. I am almost positive that your problem is that you dont have enough fuel at the point where your car is hesitating. I highly doubt the problem is ignition related.

Matt
1995 Eclipse GS
2.0L, S16g Turbo, 8 Injectors, 26psi

1998 Eclipse GSX
2.3L Stroker, AEM EMS Converted to Speed Density, FP3065 Turbo, 35psi , and so on...