Driving into the chute... can't really see what the difference would be between releasing it with the gas still on, and (very) shortly after letting off. 'Twould seem the drag would be related to the speed, and not to whether power still is being applied, being that acceleration, ACROSS the finish line is essentially zero? From the sensory standpoint as mentioned by the earlier poster that his friend gauges speed by parachute impact, I can think that timing the hit of the chute to coincide with stepping off the pedal would maximize that sensation but not be considered a "technique".
I also agree that popping the chute for any spectator appeal is a good thing; I run my car at a track I could get it stopped reliably, (probably) but if anything unforeseen went wrong it would be too late by then. I got it bouncing on the brakes once, and found that banging the helmet against the cage is painful! I will bear the burden of packing it every time. Let the turnoff bystander beware.