Strange Problem with COS Setup

[LSRacing]

Background on the car. 90 TA, 6.0L, 411PCM, 05 GTO Throttle Body, Corvette Pedal and Tac Module, 05 GTO stock intake, injectors and rail. 6 speed. Mild comp cam

The problem: Installed COS 3 and and amd a 6 speed tune from an 02 vette and started tweaking. Got done on the dyno and took the car for a ride. It is hesitating really bad in 1st gear and not in any other gear. If i feather the gas pedal, i can make it run pretty good in 1st, but, if I just go WOT, it just hesitates. Hit second, and its fine. There is no spark knock and the TP% says 100. WB reads 13.0 the whole time. Im thinking there may be a map/maf correlation problem beyond what i can change with the tune. No codes come up.

The car is N/A and made 450 HP at wheels and 460LBS tq. I dont think the power is the prob, but, the sd tune is what im leaning towards. Any Ideas out there? Thanks in advance for any feedback.

[LSRacing]

Still looking for any ideas here. I think ill try and add the MAF wiring in next and see if a MAF tune fixes the car. If it does, ill be looking for some help on how to find what is causing this.