I have a 2004 WRX with 112,000 miles. I have only had this car about two weeks. A few days ago I had a timing belt, spark plugs and fuel filter installed. Since then the OEM boost gauge will climb to .05 then drop to -.05 even with steady pressure on the throttle. Under hard acceleration the boost starts dropping before I lift to change gears. Also what should the gauge be at at idle, and when cruising at highway speed(65-70). What should I be able to build boost to? The car is completely stock(for now) except for a drop in K&N filter. I assume the battery was disconnected during service and I don't know if there is a reset or relearn for the ECM. Any help would be greatly appreciated.