My 04 GP GT2, 70k, has recently been getting bad gas mileage(down 80 miles on a tank) and it idles at 600-ish when it normal idled at high 800s. I notice a jerky acceleration at 0-25-ish and it seems to feel better at 55+. The computer is throwing a low voltage on the second knock sensor code, P0332. I have since replaced the sensor(I believe I got it down to 14 lbs, it was hard to access) and I have gotten the code again since clearing it. Any idea what could be wrong with my car?

Im going to check out the knock sensor and try to run some seafoam through the engine later this week.