Power while driving

With that many miles, it could be the engine is just wearing down (less compression from wear). However, if it seems to be something different, then I would start by checking the basics. Make sure there are no vacuum leaks at the engine, make sure the vehicle ignition system is in good condition (tune up), make sure fuel pump pressure it within the manufacturer's specs. If you need directions for checking fuel pump pressure, go to our home page under the DIY section. From there look up fuel pressure. There is a video and directions on how to check it. You will need a gauge, but most parts stores will lend them to you.