How is the valve job? Are the Ti valves sticking coming off the seat. I have seen Ti valves with a valve job where when pushed to the outer edge of the valve, on a standard seat Iron/steel seat Begin to "stick /pop" when coming off the seat. What lash is there at operating temp. First reaction is lash is too loose. Second would be drag parts being used on the street. If they are hardened tip a magnet will stick to to the tip but not the stem. If you look close you should be able to see them fairly easily.