I have an 01 Mercury Grand Marquis with 185,000 miles on it. Runs great I love the car I'd like to continue to drive it. I'm having a weird issue that the car bogs down after driving about an hour. There's a little spot in the pedal that you can feather and get the car to get up to about 50 mph but it takes forever. After stopping the car and not driving it for a while (next morning) it drives fine again. I don't ever have any trouble with it driving around town it runs perfectly starts it's just when I try to drive a long distance. It never throws a code. I've replaced my mass airflow sensor, my PCV valve, my intake temperature sensor, and my fuel filter. The fuel pump is about 4 years old I cleaned the tank at the same time and I replaced the fuel pump fuel filter and the complete exhaust system. I'm thinking it might be the catalytic converter what do you think? I'm wondering if catalytic converter cleaners work. I don't want to spend another $1,500 on it catalytic converter if I can help it. Any help you can provide is greatly appreciated thank you so much.