Has anyone tried the aftermarket carburetor's for the CS-620P on their CS 590? I have read several posts saying to upgrade to a 620 carburetor and mod the muffler for decent power gains. I have the muffler modded and was looking for a 620 carburetor and the aftermarket ones are less than half the price. I was hoping to here from someone who has already done this to see if it is worth it or better to just bite the bullet and buy the Echo? Thanks in advance!