There is a lot of info on this issue posted on this site. You need a snubber for your electronic gauge to work properly. The pulse from the IP causes erratic readings.
I have an Autometer fp gauge and had to use a snubber due to the condition you described. I bought mine locally from a company that sells hydraulic equipment. The name of the snubber I used is Chemiquip. size 1/8 porosity D. That will get ya straight. You can find them online for under $10. 00
Autometer is aware of the problem, I'm suprised that your gauge did not come with one after all the complaints they must get. Mines been on for over 3 years with the snubber without a problem. You should get it fixed quick befor you ruin the transducer.
Tim