Hi. The name is Mike and I'm new to this forum. I am in need of some technical assistance on a 1999 Jag xj8 4.0 The customer complained of a CEL and 'Restricted Performance' message. The initial DTC's were p-0171, 0174, 0301 and 0300. Initial diagnostics revealed low fuel pressure, explaining the lean codes and a leaking valve cover (oil in spark plug tube cylinder 1) replaced both valve cover gaskets, replaced all spark plugs with NGK BKR5EIX-11, Iridium plugs and the fuel pump. Drivability is much better, however the p-0300 code represents itself after every drive cycle. I've smoke tested for vacuum leaks and found none. Usint a COP tester, I've determined that all 8 coils are firing properly. Vehicle appears to idle okay. When I clear the CEL and raise idle to about 1200-1500 rpms and hold, Cel never represents itself and 'RP' message never appears. It only seems to come on at idle, and before CEL becomes constant, it flashes... Unfortunatly, I don't have anytypical data values for comparison. I'm wondering if the MAF sensor could be bad. I have cleaned it with CRC air flow cleaner and did not help any. Any ideas on the matter would be appreciated. Thanks in advance.