I have a 2003 Outback 2.5 cylinder that has 231,000 miles on it and it began vibrating when accelerating last week while on a road trip. It isn't all the time during acceleration, at a particular speed, or RPM. I can tell it is when I am trying to push up a hill or just a little more gas. I don't think it is plugs. It isn't bad yet but I needed a new axle as well so I took it to the dealer so they could diagnose the problems for me. They agreed that I needed a new axle and that I needed to get my catalytic converter replaced. I did have a couple of error codes that indicate a problem and I have seen several posts about the P0420 code. Some say that it is the O2 sensor and others say the cat. I replaced the O2 sensors about a year ago so I don't know if that would be the problem. Before taking it from the dealership, I asked them to reset the codes for me. I have been driving it around all day and the CE light hasn't come back on. Anyway, I don't want to drop $1000 on a new cat for this old car and was wondering what the consequences would be for taking it to a muffler shop and have them remove the cat and running a straight pipe. What do you think? Will this impact the gas mileage, performance, sound, etc.? Do you have any other suggestions?