I have an 06 dually with 6 inch bullhaulers, no cat, no muffler. It sounds great, but sometimes its too loud, like when I'm towing a trailer. What I want to do is have the best of both worlds. I was thinking about installing a Y pipe somewhere after the downpipe, then put a butterfly valve on each side of the Y. On one side (behind the valve) I would put a muffler, on the other would be a straight pipe. Then there would be a y pipe after the muffler/straight pipe to bring the exhaust back to one pipe to go up through the bed and out the stacks. This way i can open the muffled side and close the straight side if I'm towing a trailer or vice versa if I want to be loud. Clear as mud, right? The trouble I'm having is locating 4 or 5 inch butterfly valves (electronically or cable controlled). Its a fairly simple part, especially if its cable controlled, but I cant seem to find what I'm looking for. I remember seeing a vendor that had what I wanted in a Dieselpower magazine a while back, but now I can't find the magazine that the advertisment was in. If anybody understands what I'm trying to do and can help, I would really appreciate it. Thanks in advance. Oo.