I've recently purchased a 2003 Cobra with about 66,000 miles on it. It has just the basic mods; pulley, x-pipe, cat-back exhaust, CAI and Diablosport tuner. It runs great and is very responsive, until it hits about 5,000 rpm and then it falls on it's face. The first time it happened it felt almost like a rev-limiter kicked in. I pulled DTC P0148, so I changed the fuel filter with a Motorcraft filter (pulled out a Purolator...ugh) but nothing changed. From what I've read the FRPS is a pretty common problem, but it seems like people usually have more severe problems, like not starting at all or running horribly. Same with what I've read on the P0148 code. This car starts and runs great, just until it hits higher rpms. Any suggestions?