You severely overdid it on the valve stem seals. "More" is definitely not "better" where valve stem oil control is concerned. Chances are you have badly worn valve guides now due to the valve stems being starved for lubrication. A small amount of oil down the guides is necessary to keep them from galling, particularly on exhausts. I'd suggest removing the head and finding a machinist who knows what he's doing- - - -and maybe pitch that "lump port" head as far as you can throw it. That's a racing modification that has no business whatsoever on a street driven vehicle. It's only useful at throttle positions and RPM ranges the average street machine never sees. Have you done a cylinder leakdown test to evaluate the sealing ability of the rings and valves? The slogan that used to be on every piece of diagnostic equipment Sun made back in the 1950s and 60s was "We Test- - - -Not Guess!"
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!