Hello All!! I recently bought my first first Honda ever and well it so happens to be an Odyssey. Its a 1999 that looks almost new inside and out but the catcher is it doesn't run and someone cut off the cat convertor. My question is does the cat provide back pressure to the engine needed to have it run properly. It seems like I read somewhere there are engines that require exhaust back pressure for proper operation. I ran a compression test on the front cylinders and they were all three right around 140 psi but I think the engine has to be warm to get a good reading. Insight would be great!!