Would slip-ons alone cause the motor to run even more lean?

 

They very well could. I can hear my RK box stock decel pinging in the stock mufflers. Not on a throttle chop. But just a gentle decel. And thats with pure 91 gas. No ethanol. I need to poison it and see what it does with crap gas before I put my stage 1 on it. It might calm down the decel ping pop it gets but make it accel knock. I hope Trump all but kills the epa and gets rid of crap gas in free states.