My opinion- If a closed chamber OEM head will make the power you want AND if the cost to refurbish them comes in at say $900 then go this route. Its recommended that every aftermarket head whether its an el cheapo whatever all the way up to big time $$ great brand heads that you pay to have a shop completely check them out and correct everything. For $900 to have your heads redone you know they correct and ready at time of pick up.