If dropping in pulley size, it's highly recommended that you scan so you can see how much KR has been introduced.
Anytime you drop in pulley size, you're introducing KR, even with a reprogrammed PCM.
I scanned at 9* KR, WITH a reprogrammed PCM, a different reprogrammed PCM gave me 4-5* KR, a third PCM (my current) has given me nearly 0* KR.
Every car reacts differently, that's why it's recommended scanning when dropping pulley size. Someone on CGP dropped a pulley size and scanned at 0* KR, with a stock PCM, obviously a factory freak.
Not scanning when dropping pulley size is being brave. It comes down to how lucky do you feel.
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Bobby
Died 5/1/08, resurrected 5/15/08
ASCD SD hood, 17" Bullitts, Overkill PCM, 3.4" Pulley, NGK TR55IX, K&N 9" cone filter, JimmyC D/P, U-bend removed, Flowmaster 40 series, Hooker big bore tips with resonators, S/B brake lines, drilled/slot rotors, GMPP handling kit, KYB struts, F&R strut supports, HID's, LED's, 2.5" Air Dam, red GTP overlays on custom badges, white rear insert.