I have an 84 Monte SS with an 87 Gn motor with 009's, bigger cam, TH 3" downpipe and ATR SS dual exhaust. Had a TA 61 on and was sluggish. Switched to a TA 60 and was about half way between the 61 and stock turbo in spooling. Really not that bad with stock converter. Didn't like the 61 at all with the D5. 61 pulled noticably stronger after it spooled up than the TA 60. Both are .63 housings. Car ran 12.60 @107 last week on street radials (not drag) 93 Octain and closed exhaust. This was at Salem, Ohio, a 2 tenths slower track as it goes up hill at the end!