I know from personal experience that the 58 mm throttle body(on a STOCK internals) will cost you about 2 tenths at the track and about 1-2 mph. I have ALL the BOLT ON goodies on my 350(SLP runners-Air Box/Edlebrock headers and intake/MSD//BORLA/Air Foil/prom chip/160 stat and more. I was running 13.9 to 14.0 @ 99 mph. After I put in the 58 mm throttle body, the car was running 14.1 to 14.2 @ 97 mph. Needless to say, in went the STOCK throttle body. You WILL need the SLP fresh air box plus a 160 degree stat and a Hypertech 160-172 degree fan switch to keep that heat sink cool. 
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1991 FORMULA 350-GONE BUT NOT FORGOTTEN
1 of 1,197 with L98 Option/13.79@100 mph
1994 25th ANNIVERSARY TRANS AM GT -1 of ONLY 2,000 made/ Only 128 made with a HURST 6-Speed Manual and 91 with T-Tops and Compact Disc/ K & N Filtercharger/Magnaflow Performance Muffler/Air Foil- ORIGINAL MINT Arctic White Ultra Rare SURVIVOR. DAYTONA 500 PACE CAR Decal Kit!
SOLD: 1989 Turbo T/A in 1991 it ran 12:18@115 mph
Last edited by edpontiac91; 01-02-2008 at 06:29 PM.
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