Need some advice !!

Ive installed my Sn 92 and get a solid 5psi boost . Heres the kicker, Iam slower with the blower than without.!!! I have to back timing out so far that I think I loose all that I gain.iam at 29 deg total timing from 38degs. Iam thinking that I have to much compression( maybe my gauge lies to me ) Iam at 9to1 on this gauge.Heres some specs...355 sbc, 780Holley 74front 83 back plus powervalves front&rear,194/160heads,headman shorttys,2.5 inch exhaust throughout,3500stall in a turbo 400,3.23 posi,3100lbs vehicle...........Help!:confused:

Also. this is a Drawthrough setup! thanks for any help