340/360 intake choice for high 11s
Just remember for best et. you need to set up the hole car, rear end, trans, eng and elect. and tires. and what length track. 1/8 or 1/4. my car runs the same on both the rpm air gap and single plain M1, it seems that the M1 is better in the mid range and is more consistent . what ever is less expensive go with. Good Luck Gary