Pete,
Quite simply - do not waste you time with a t34!

However, you are your own man and i have had all 3 well known variants of the t34 before moving to the 3071

t34.48 - quick spool up. Cracked exhaust housing around wastegate penny on my stage 3 setup. approx 1.6 bar. Boost tailed off, but sod all lag between gear changes.

t34.55 - not sure why i bothered with it tbh. I listened to rainbird and while he was in fact correct about it being better than the 48 for top end power it was virtually the same as the 48. Same spool up from memory, no lag between gear changes and slightyl better puff higher up the rev range.

t34.63 - was expecting the worst as every expert *cough* out there says laggy as fuck, undriveable, would piss me off blah blah. UTTER horse shit. Slim was correct as per. By far the best exhaust housing on a t34. Ok slightly longer to spool but peaked at 2.5 bar and holding 2bar (maybe a smidge under) to approx 6700 rpm. Came in with a huge shove in the back and i wish i hadn't spent £300 of my hard earnt on the 55 but never mind.

If you must have a t34 get the 63 housing. But if you dont have to get a t34 get a 3071, some bigger injectors and away you go. Forget t34's and t38's. Yesterday's news imo.