Hey guys i have a 98' GT and the only mod is it has flowmaster axel back. She is having problems starting. But eventually does after about ten seconds on second crank. It also drives perfect in the city and i can hot rod all i want but if i go on the highway like an hour away it will start to bog down and loose power when im on the highway. It also surges if i try and push the pedel in on the highway. The Check Engine Light gave me codes for EGR valve and upstream O2 sensors so i replaced both of those and problem was still there. Cleared codes and now im getting EVAP purge sensor error and now BOTH O2 banks are running errors. Still having exact same problems. Put a pressure guage on the shradder valve on the fuel rail and got a fuel pressure spike when turned the key to ON but than pressure goes down to "0". When car is at idle than pressure was perfect. I didnt check at high RPM. Any input would be greatly appreciated because i am lost on this.