Might as well figure that any cylinder head made for passenger cars and trucks after 1974 is a smogger head. If you want good heads for performance forget the stock stuff and get the aftermarket aluminum or cast iron heads. The last few years the factories have finally put some performance back into their engines, the small V-8's are fairly good the way they're made. Now add a blower and upgrade the electronics and it's easy to get in the 400+ horsepower range with nothing but bolt ons and plug ins....