The muffler really needs no modification at all. The deflector or "guide" as it's shown in the IPL came in several different flavors for those saws. Early 600P's will have a very small guide and separate deflector with a screen under them. I haven't seen a later 600P yet, but they share the same P/C as the CS-590 and are likely to have the later deflector/guide which are spot welded together and very difficult to separate.
The only modification that needs done is to remove most of the material on inner guide and leave the outer as-is, so the exhaust port in the muffler has a straight shot
A few weeks ago I ordered all the "guides" listed in the IPL for the CS-590, 600P, and 620P. Interesting that the completely WRONG part showed up for the CS-620, but was packaged correctly with the correct part number on the package.
The 600P part showed up as the later part used on the CS-590, not as two separate parts shown in the IPL. The later part will be taller and larger than the original that was used on the 600P, and it will be tach welded together. I attached a pic of the original CS-600P part, side by side with the CS-590 part.
Notice how much larger the CS-590 deflector is compared to the CS-600P.
I tested my 600P with the original smaller guide against my 262XP and it was just a tad quicker in timed cuts. I have since installed the new larger guide but haven't repeated the testing. In any case if you 600P has the early two piece design all that you have to do is remove the inner guide/deflector. The later type may need ground out as shown in the pic below. I tried to separate one of the ones I purchased and it was NOT coming apart without destroying it.......Cliff
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