Stock makita 6421. I ran it stock first then split the muffler and removed all the cat junk inside and ran it same chain same log. Didn’t even touch the carb settings lol. It gained 27%. After doing this little test, I honestly couldn’t recommend to anyone to get a port job for a 6400/6421. Some saws don’t even gain this much from a full house port job. I have a 6421 myself that I ported, it gained good... was a fun build. But it wasn’t really worth the time for the gain over the muffler mod. If a guy wants more power from this chassis... spend the money you would on porting the 64cc cylinder for a 79cc 7900 cylinder. Then port that. Lol