89 with a lean condition

ok need a little advice here, this is my set up i am running a 302 with gt40 heads 1.6 roller rockers and crane valve springs, gt40 upper and lower intake
trickflow stage one cam 24lb injectors 255lb fuel pump, powerdyne 6lb kit. "no fmu" adjustable fuel pressure regulator. accufab 70mm throttle body when the car was built we put it on the dyno it pulled 405rwhp but was leaning way out. my quastion is why and what can do to fix this issue with useing a t-rex....i have many other cars with almost the same setup with no fuel problems.

thanks
rich

i have the boost sensative one i remebr the guy at the shop stressing that and as a matter of fact we actually used it to kinda fix the problem. but i still have the issue.