I've been tuning my Holley 4777. I'm running quick fuel metering blocks. I've the Idle feed restrictors dialed in and it runs best with 40IFR's. All was good untill I put my new flowmasters on and now I have a miss at highway cruise speed (65mph @ 3100RPM) I can speed up a little and it will go away, if I back down it misses all the way to about 1500rpm. Do you think its jetting (71 prime 81 sec), timing, or need to increase the IFR's again. Like I said this started after the new mufflers.