I'll take a stab at this, boys!
I am VERY familiar with turbo Buicks. My old Turbo T/A was built by ANS Performance, and I also used to be a dealer for ATR. I think that qualifies me.
TurboSix: You are already on the right track...
1) Buick pushrod, 2-valve heads hate high rpm unless reeeeeally massaged. Most stockers redline under 5500rpm, and most mildly modded Supras pull to over 7000. My Turbo T/A ran high 11's, yet I shifted it at around 5400 for the best ET's.
2) The Supra 2JZ-GTE cylinder head is VERY efficient. It flows gobs of air in stock form, and tons in ported form. A cylinder head that moves a lot of air needs a lot of air. Hence, the bigger turbos.
3) Lag, schmag!!
I don't know about you, but I like to go FAST. So a big turbo doesn't reach full boost until 4500rpm. So what? Who the hell races full-throttle and shifts at 4500rpm? In my case, as is your Buick, you have an auto trans. CONVERTER, my 6-cylinder friend. Put your foot on the brake, step on the gas, and you will rev freely until the boost builds up. I got your lag right here! Even better from a roll. Just punch it. Duh. Trans kicks down a gear, tach hits around 4000rpm, and WHOOOOOOSH...
4) If you are looking for a good-performing Buick turbo, but something you can run a mild converter with, try out a TE60 or a TE63. Should be good for low 11's to high 10's with the right fuel, EPROM chip, and exhaust.
Happy boosting!
