Odd issue with car after Whipple install

[99FiveOh]

So I installed a 2.3 whipple last week and had it tuned Saturday. The A/F was jumping around a little but he got it settled down and it ended up putting down 589 rwhp and 554 tq. So I go to drive it and it had some detonation at higher rpms. I don't have an aftermarket boost gauge and his was broken so we don't know the boost but given the power it made I'd say I'm around 16-17 psi.

Fast forward to today we put it back on the rollers and the A/F is jumping around, meaning one run it's 10.0 flat all the way across then the next run it'll lean out. I swapped to a return fuel system consisting of twin Walbro GSS342 pumps, modified stock hat with new wiring ran to the pumps, dual relays, -6 return line, Aeromotive regulator. I stood and watched the fuel gauge while he made a "lean out" pull and the fuel pressure went up as it should. I recorded it with my phone and he looked and said it was right on.

MAF is a BA3000 and injectors are Ford Racing 60 lb injectors. The TPS shows full sweep as well.

I ended up leaving the car with him as it got late. He is stumped. Everything seems in order but something is causing the A/F to jump around run to run. Doesn't make sense. If anyone has had this issue or has any input I'd appreciate it.

 

[99FiveOh]

Wanted to mention that when the A/F changes he does absolutely nothing to the tune. Does anyone know what all in the tune has to be changed when going to return?

 

[R3dfireCobra]

I see your in Jax, who is tuning your car?

 

[R.D.P.]

What pulley setup? I'm not saying it's causing the issue - but I would want to know what boost the car was seeing. There have been people that have seen anywhere from 14lbs to 20lbs on a 2.3 Whipple with a stock lower and 3.00 upper. If you could see the boost level, you might see that boost is higher when you are leaning out. You could have some belt slip, so some pulls it's slipping and the car is getting less boost, then the next pull it grabs and higher boost.