00gtr1

If it is the trans the overdrive light on the dash will start to flash. And it will store a code. With that many mile i suspect the direct clutch its a common failure on higher mileage units. Now my experience with plugged exhaust is this usually the ones I've seen if the exhaust is plugged the car would hardly even run at all. especially escapes because the cats and exhaust manifolds are one unit. Now how has the vehicle been running up to this time? has it been missing? or has the check engine light been on? if you have been driving around with an ignition miss unburned fuel gets trapped in the cats and melts them. Also prior to a cat failure the check engine light would be on and u will get a P0420 or a P0430 codes, those are catalyst system efficiency codes. hope this helps keep me posted