Question about timing in a SC car

When I had my car dyno'd it only made 350 hp to the tires and 373 tq @ 12 psi. The tuner said that hey locked the timing at 18* total due to the fact that my ACT sensor was before the blower instead of after and he didn't want to risk detonating.

My question is, what is the norm on total timing on a Vortech'd 5.0? This car has the exact same mods as my old 95 S-trimmed car and made only 1 less lb of boost but was way down on power compared to it. My old car made 425 to the tires @ 13psi so I was expecting similar numbers.

So does timing make that much of a difference? I didn't think to ask him to pull my old tune up and see what it was making for total timing. If any of you self tuners have a supercharged car, what total timing do you like to run at? My base is only set to 10* as advised.

It's a completely stock longblock. The only mod I have on the motor is BBK headers and Eddy performer intake.

Anybody know what the normal timing pull scale is for ACT's? For instance if the ACT gets up to 200* how much timing should the computer be pulling from total timing?

I'm asking because I may get myself a QH and try my hand at tuning myself. I think I can get my tune file from the tuning shop to play around with.

It's been relocated, I went back and only managed 370/400 @ 15 psi because the computer was pulling my timing down to around 12-13 degrees. I need to cool it off now and I should make a ton more power!