It is a very controversial topic for the Barra, Porting and cams lol. I am looking at chucking 5k into my head in the next month which consists of, Full CNC porting, Valve springs, Custom cams, Machining seats etc, Kelford cams would be doing the work, the last head they did they unlocked another 40CFM on stock valves!! But now I am second guessing it, 850KW @40psi is pretty good going for a stock head.