FT & full boost hesitation symptoms

[DGraber460 at aol.com]

As I spend more time driving and "feeling" the performance characteristics 
during all conditions, it seems the car is flattening out at 4800-5000 RPM in 
first gear only, and a slight hesitation at about 4200 in second and then 
pulls well in third & fourth. This is repeatable. If throttle is applied more 
slowly after driving (and stopping) for more than 20 minutes, it doesn't 
appear as pronounced. Does that point more clearly in any direction?
Would the lower gear give the turbo the ability to bump the FP cutoff more 
than higher gears? I'm running a stiffer spring screwed down by an adjustable 
cap without a chip (13.5 psig, Denver altitude). I'm grabbing at straws here, 
but unable to find a logic trail.
After adjusting the fuel pressure via the screw in the bottom of the FPR, I 
have it set at 51 psi, and that gives the best power in all ranges. I tried 
it at different pressures from 43 to 58.
TIA

Dennis