[IROCZman15]

good point, yea actually I can't tell if its the fact that I can't really get a strong brake pedal press creating the line pressure, or if its just that the drag radials are getting sticky during the burnout and overpowering the front brakes.

the way it "feels" to me, is that when I press the brake pedal and activate the line lock, its only moderately pressurized because the lack of vacuum (7.5") feeding the booster isn't allowing the booster to do its job properly, so in turn brake pressure and line pressure at the caliper is minimal.
-- I could be totally mis-thinking this, so if anyone knows, feel free to explain it better to me. All I know is that with the old TPI engine I could line lock the car 1st-2nd-and into 3rd gear and it would hold my extended fun burnouts. I had proper vac to the booster then, and now, not so much.

A test/solution I wish I knew about before winter arrived was to put the car in neutral, revv up the engine high, and let it drop down to create vacuum on the brake booster, then put the car into gear and line-lock it (or launch it). Apparently some guys with similar setups like mine will do this. Free rev the engine while on the starting lien in neutral, build that vacum as the throttle blades are closed, put it into gear and footbrake stage the car, footbrake launch. I had never tried this. I was launching from a low vac idle and pushing through the brakes. same for linelock. never free-revved it prior.