All the dyno tests on the C&L plenum are on 99+ gt's with PI heads of course and I'm sure everyone has already seen what I'm about to say on the c&l site but maybe some didnt so heres the link and they get decent gains on an almost stock 97 GT and they say mac Throttlebody but dont say the size...hmmm heres the link
http://www.cnlperformance.com/plenum09.html