Hey guys, I have a Toro WB that sat for a while (previous owner). It runs great and all but I see varnish collecting in the fuel filter. I really think I should clean out the gas tank and am wondering how to do it. I plan on draining all the fuel and then taking the tank off. What chemicals should I use? What is that stuff that yer supposed to put in it that has rocks in it and then shake it all around to loosen the gunk and varnish? Any advice welcome. Thanks.