race veterans plz help!!!!!!!

I beleive the Street avenger is a vacum sec. carb No?You could try changing out the secondarie spring(different colors)which will change when your sec. open.Now for my 408 I race with,I run an AED850DP(modified holley)which Summit now carrys for a reasonable price IMO.I bolted it on right from the get go and ran 11.20@121mph,now my best has been 10.81@124 60fts 1.50.Now my engine setup is different than yours,so need more info on your setup.
Ignition(MSD)?
Intake and cam
Tire size The 2.6 60 fts sounds like it,s falling flat on it,s face.