I own a 1995 5.0, and have been having a weird problem. When the car is up to temp the car is missing at low to moderate RPM'S under load. Runs ok when the vacuum line to EGR valve is plugged. Replaced EGR valve, hooked up vacuum line and the same problem occurs.......It still misses. After driving and then letting the car sit for a while, and then starting the car back up the problem still occurs. Any suggestions? Please help. Thanks