04sm450r valves

I could use some help. I just got this bike (04 SM450R) at the beginning of Sept and went for one short ride. It was popping on decel so I thought I had a lean issue. Long story short I have stock jetting, 175 main, 30 pilot, I turned air/fuel out 2 turns and since I had the bike apart I check the valves. Intake is dead nuts @ .006, but the exhaust is zeroed out. I was told that the bike has a 05 head on it which I believe to be true because the shims are a 9.xx diameter where the 04 shims where a 7.xx diameter. Even with the shim removed on the completion stroke I cannot get a .0015 feeler between the rocker arm and the shim holder. I saw a thread saying something about the decompression may have an influance but I can’t find the thread now. Anyone have any Ideals or tricks to try and eliminated possible causes?
Thanx