I want to go as high as I can on boost with 91 octane and a tune to compensate. What size pulley should I go with? What kind of gains can I expect? I have the 3.4" that came with it right now.

 

I would go no smaller than a 3.0 pulley. I know when I went with the 3.0 on 91 octane, I had a ton of detonation and resorted to a 3.25 pulley.

The tuner (reputable) could not get the knock out, even with minimal timing. A 3.0 pulley is going to spin your blower faster and create more heat. I seen 180 IAT's after a dyno pull with Setrab exchanger. If you dont have the upgraded heat exchanger, I would stay with the 3.1 or 3.25 pulley. 8-9 pounds of boost.

I would also make sure your exhaust can support the flow of your supercharger. My 3" in/out Magnaflow did not support it and my truck quit making power after about 5400 rpm's.

I may be the exception here, because when I asked, everybody said that a 3.0 would be no problem. The best of luck to you man.

 

I would go no smaller than a 3.2 without any methynol. I have a 3.2 and see 9lbs at full throttle and 10lbs for about the last 400 rpm's.