Try downloading the
"Jetting Calculator" from Pat's site. It's a good place to start. I threw your info in it and based on stock Pilot Jets (42), the calculator comes up with 158 Main Jets at your altitude using "open" pipes. I'm guessing the 12" shorty's you mentioned could be considered fairly "open"
The aforementioned executable runs alone on your OS and is virus free.
Regards,
Tom
