Need help tuning, i think

as far as i know. i have a stock 350, with roller rockers, weiand 142 blower hooker comp headers. the carb is a 600 cfm edelbrock. i also have a full msd ignition setup, msd 6 box, and pro billet distributor,as well as msd coil and 8.5 wires. i just bought new ac delco plugs,and gapped them .040 .heres my problem. we took it for our first test drive tonight. there was a lack of power. so brought it back, checked the timing. we was -4 @ 10 degrees on the timing light. so we tweaked to be right on 10 degrees. is this where it should be? i thought i seen that somewhere.anyways its very accurate the timing isnt jumping around or nothing like that. so we took it back out, it helpped, but just still isnt there, almost like the 4 barrel isnt kicking in, so we checked to make sure its opening up, and seems to be opening with the engine off, so should work running. we did however find one small vaccum leak, i forgot to plug one of the small ports on the carb, but surely that isnt it. am i doing this right? i set the timing light @ 10degrees, and then set the crank at 0 on the timing marks, right?? how do i check,or adjust the ending timing? or what else can i check. im kinda lost. i have a 700 cfm holley carb to put on it,if need be, however i didnt really want to, as i was planning on selling the car. any help would be greatly appreciated. im lost. thanks alot.
phil

oh the car is a 91 rs auto trans, 410 gears.thanks

How much is that blower pushing? .040 may be way too big even though you have a pretty good ignition setup. That's one of my first thoughts.

im not sure how much boost its creating, i dont have a boost gauge,and im not even sure where the port for it is??? the blower is listed at 4-6 lb avg, boost.we tried adjusting the timing a little more, and cleaned up some of the wires from the msd box, it seems to run a lot better, however the roads were kinda wet out tonight, so i wont know till it dries up some, what do you think i should gap the plugs to? the factory box says .035 thanks

I'm running 7psi (equivilant of about 5psi @ sea level) with a MSD 6a, blaster coil, and 8.5mm superconductor wires, and I'm gapped at .035 and spark is blowing out. Before the MSD I was at .021"... I think I'm gunna regap (again...) to .025-.027".

Honestly at this point I'm not seeing any advantage to running as big of a gap as possible... it kind of either ignites or it doesn't, and its nice to have some leeway for different driving conditions.

thanks alot.
ill try to regap them today,and see where it ends up with that. the plug im running is supposed to be 1 step cooler also from the factory plug. thanks again for your time.
phil