I was told by a mustang cobra guy that if i got ported heads that flow 271 .600 it would make me lose power all over and i have xxxtune hooker lts y catback ls6 intake on a 99 transam m6.......the heads have been milled .15 and have 918 springs.....andi was also wondering if its ok to just bolt in milled heads i believe the heads are from a 99 ls1

 

That makes sense. He drives a mustang. Increased air flow does not result in a loss in power. I'm not sure where he took physics or learned about motors. Now as for how much you will gain, that's another question. The stock cam can only utilize so much flow. And yes, it is possible to just bolt on milled heads.

 

Don't listen to that guy and I would check PTV Clearance just to make sure.