Is there any way to minimize porpoising on autopilot by changing values in the aircraft config or air file with aired? If so, what parameters should I change? ThanksMurrell

Usually an indication you weren't correctly in trim before engaging the a/p, as it erroneously uses trim to control the flightpath.Allcott

...it's also a symptom of "flying too fast" IOW, exceeding the Vmo for the aircraft type certification.