The latest mods I have done, to my Holley is plugged the power valve and jetted the primaries to 65 and secs to 73 running alot smoother but need to get 68 primary jets. I read a post on mazspeed.com who says to plug the power valve and run 68 prim's and 72 sec's and that is for the 600 on stock port/street port 12a's and 13b's. This current set up is running the best so far for me, but havent had any track time. maybe tomorrow if Iam lucky?