To answer your question about what KR is. KR is "knock retard." The engine has knock sensors in it that can hear when the engine is getting spark knock (predetonation), which is when the mixture in the cylinder ignites before the plug sparks. It retards the ignition timing when it hears this knock to try to reduce this spark knock to save your engine. Spark knock if not controlled can damage your engine badly. KR is a good thing for your engine, but bad for performance because it gets rid of timing. With a 3.25" pulley, the blower will be making so much heat with your mods that it will cause the mixture in the cylinder to ignite before the plug sparks, causing KR, pulling your timing, and therefore slowing your car down a lot, therefore basically getting rid of any gain you would've seen from the pulley. If you don't plan on doing any more mods than what you have, a 3.5" pulley is as small as you want to go. You might even see a little KR with that pulley, but it will probably only be a degree or two if you do which can be destroyed with colder plugs or something to that effect.
If that didn't help you understand what KR does and why it is both good and bad, then I can link you to a great article about it that should make it really clear.
1990 Maroon Grand Prix STE McLaren 3.1 Intercooled Turbo, 14.695 @ 94.49 on 12psi before cam/heads/etc.
1990 Bright Red Grand Prix McLaren 3.1 Intercooled Turbo, 14.819 @ 92.72, 189whp
1999 Grand Prix GT 9.75:1|K&N|160 tstat|No Ubend/Cat/Res|UD Pulleys|Ported M90/TB/Heads|XPZ|2.55"|Pacesetters|Stage 2 I/C. 12.442 @ 112.78
2000 Blue Bonneville SSEi Supercharged Gutted Airbox|K&N|3.4"|1.9'*|WP Pulley|Custom DHP|180*stat|41932'*|No Cat. 14.681 @ 94.80
2002 Dark Cherry Grand Prix GTP Supercharged & Intercooled
12.084 @ 114.38 w/1.743 60', 315.6whp, Fastest Stock Cam M90 GTP!
NOW XP CAMMED, 340.6whp with XP, stock heads, Gen 3 M90, 11.984 @ 115.84 w/1.750 60'!
Most HP Stock Heads Gen 3 M90 GTP!
2004 Red Monte SS Supercharged K&N|3.4 Pulley|1.9'*|180*stat|41919 plugs|3" dp|No cat/ubend|DHP|Shift Kit. 14.2 @ 98
GOT BOOST??? Friends dont let friends drive stock!