"just because it is louder doesnt mean it is faster"
Agreed, power is NOT measured by noise level. It is measured by timed cuts before and after the modifications.
I've modded a couple of my saws, and did timed cuts with several of them, with positive results.
I make very small mods, blending and smoothing things our along the way, etc. I do not and have not touched any of my older saws, as they are pre-emissions, already loud enough, and have PLENTY of power at every rpm.
From what I've seen, the newer saws respond well to opening them up just a bit.
Spefically, I have muffler modded by Echo CS-510, CS-520, both CS-370's, the little Ryobi and the Echo CS-360T.
I did timed cuts with the Echo CS-510 and one of the CS-370's. Then I went on to run them back to back against other saws with similiar size engines, all with positive results.
The CS-510 outran my Shindaiwa 488, and tied my closed port Husqvarna 55, which is a very fast cutting saw.
The CS-370 with a muffler mod outran a stock CS-400 by 7 seconds for 5 timed cuts in the same log with the same bar/chain set-up.
The CS-360T responded quite well to a muffler mod, but was not tested before or afterwards. It simply ran OK before opening it up, but pulled down easily under heavy load. After the muffler mod it pulls harder in the upper rpm range, and doesn't pull down or stall easily against the clutch like it did before modded. Certainly not a "scientific" test, but I ran it quite a while before modding it, so I can tell the difference......Cliff