You used a billet 71 hpq and the billet 67 HPQ correct...? Biggest difference in your opinion? What would you say a Buick must have to use the 67HPQ properly?
I have a billet 71GTQ and tested the billet 67/68. Never put a HPQ on my car, just haven't had the opportunity.
As far as 67 goes, it all depends on your combo and what you want to achieve. It's a 11 second turbo or an 8 second turbo, depending on the rest of the car.