Posted 15 August 2017 - 09:14 PM
@mhub91 the porting is free; as stated the valve seat when pressed in the head protrudes into the port choking it off by 2mm, you,can use a dremel or rat tail file and simply get the valve seat flush with the port wall. That and matching the intake gasket to the port and the head will net you 5-8% increase. A reground cam and lifters will set you back $125-$140. If you shop your local Craigslist you can find a Yoshimura or Borla muffler for $100 after that you just need some 2" tubing, any muffler shop can weld it up.
I can't remember the exact price but when I did the head on my A15 I used the reduced neck valves from SI I think it was around $125 to $150 for the set of 8. I don't remember the exact difference but the stems are 1-2mm smaller diameter and swirl polished. They are a cheap upgrade that doesn't take anything away from the reliability.
Besides the SI valves you can also use the .80 thick (versus 1.2) head gasket will up the compression
So there are some of small things you can do to pick up a couple of horsepower here and there.