Every FI motor ive seen, especial turbo set ups seem to accumulate much more carbon build up as Stewie mentioned. The only way a valve adjustment will effect comp numbers is if they are too tight to seat fully, or in Stewies meaning, because there is a crap ton of carbon build up and the valves are sticking/cant seat fully from that, hence the sea foam clean.
That said, this is only under the premise that comp irregularity are not from compression ring wear. Only way to determining that is to do a leakdown test. That will tell you right then if you have any valve seating issues.
Last edited by s2000Junky; 03-05-2017 at 02:39 PM.