About 6 months ago my fuel pressure started reading low. Less than .5 lbs without the boost on. Boost brought the pressure to 5 psi. I replace the sender and got the same results. I added a mechanical gurage and found that the Dynon is reading about 1 lb low. Measueing the resistance across the sender (not hooked up) I read 11.9 ohms. How can I fix the 1 lb offset?