The tail pipe and muffler are rusted and need replacing. I've seen somewhere a 2.5 pipe, put a single cat and muffler were recommended as the way to go. What do you guys think would be the best setup. It's a stock 1988 FJ62. At some point they would have to merge the two pipes from the exhaust manifold right? Would the diameter of the head pipes stay the same? Imput please. thx clone