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http://img254.imageshack.us/img254/3950/19jf4.jpg


Something like this?

Is the inverse, confirm here http://ctny.audiworld.com/mark/s4/gears/gear_calc.html

Lower ratio = more speed.

Check on turbo elbow if your s13 have one oxygen sensor.

About the rest, can be many things.. but basicly the engine slowdown after warm up?

Cometic and ARP bolts will be perfect.