The center muffler on my 87 300e is rusted out. The PO replaced the oem rear muffler with a resonator & welded the unit instead of clamping it on. I'd like to keep the resonator, but how do I know where to cut? Also, can I use a hacksaw or do I need something else? Autozone will do the pipe end expansion for free, which I guess will be needed for the resonator pipe to go over the center muffler pipe. Thanks.