I'd have to go on a treasure hunt to locate my M1 stock vs modified intake tests cuz I don't recall where that stuff is now. But to Dwayne's point, any time I've added an intake to a head on the flow bench, the intake always dropped the head-alone flow numbers a bit... some more than others.

The question about the hood clearance was for the same reason as Andy commented: if you don't have a hood clearance issue, switching intakes (Trick Flow or mildly modded Victor) will likely get as much of an improvement as putting $ into porting a 4150-type M1 intake. You could drop $500+ in porting labor and maybe pick up 10 HP, or you could drop $500 on a different intake and probably pick up just as much, plus you can sell the M1 to recoup some of the cost. A full-blown porting job from Wilson is gonna be 3 or 4 times that much, but they'll probably get everything out of the intake that's possible.