Dan, most manufacturers use the crankshaft sensor to determine if a misfire has occured. The PCM knows through its programming that each cylinder should produce a certain amount of push on the power stroke. When running at some RPM, the PCM knows what the time should be between each cylinder firing under normal conditions. When a cylinder is not doing its job, the rotational velocity of the crankshaft slows down. Each cylinder's timing is stored in a separate accumulator in the CPU and compared with preprogrammed tables to see if a fault condition has occured. When value(s) are different, a MIL is set. The PCM uses the camshaft sensor to determine which cylinder is the culprit.
When the vehicle is traveling over an extremely rough road, the wheel(s) is off the ground for a short amount of time, causing the engine RPM to fluctuate somewhat. This is usually detected as a P0300 (intermittent misfire) since the rotational speed of the crankshaft can happen at any time when the tire(s) leave the ground. Of course, having a P0300 code doesn't necessarily mean excessive road conditions caused this. This is only one possibility for this code. The PCM is only saying that multiple misfires are occuring randomly with the cylinders. So, other factors which could affect all cylinders such as a lean or rich condition, bad wires, bad plugs, etc are possible. Also, transmission codes can be set when an intermittent misfire is detected because the transmission uses the RPM of the engine as one of its inputs to determine shift points.
Since an engine misfire really didn't happen under road conditons, some manufacturers are monitoring the firing voltage of each spark plug to determine if an engine misfire really did occur. For example, if there is a lean condition in some cylinder, this will raise the firing voltage and if the cylinder is rich, the firing voltage will be lower. The firing voltage can also be monitored for other conditions such as a bad wire, fouled spark plug, low compression, etc. All of these conditions can be monitored to set the MIL. In this way, road conditions will not set intermittent engine misfires.
As for your codes, I would suspect that you have two separate conditons. One is for your TPS and the other for the EGR system. I had posted a technique to check out the TPS with a DMM that may help you out. It's located here...
http://www.automotiveforums.com/vbul...7&goto=3548067
Hope this helps you out!