I have tried with the caps on and off, I didn't find any difference, but will put it on the rollers again to check, also going to check airbox versus cone/cone with shield.
T34.48 will do more than 380 without problems, CR turbo's man used to run this on his 2wd cossie, but lightly ported head, works wonders on these particularly at top end, where as said they don't tend to run out of puff so easy.
I am going to a T34, with a .60 ar comp housing as I have std T3 comp at the mo machined out to take t34 trim, so it has an easier time.
tabetha