99 Mercury Grand Marquis LS 140,000 miles

A month ago my car started but could barely drive over a speed bump. In made the corner and stalled. Replaced the fuel filter & fuel pump & reset inertia switch and it fired right up and was running great but started making that wailing groaning noise so replaced the IAC Valve and was running great but 2 days ago it stalled and won't start. Inertia switch wasn't tripped and getting fuel to the rail. Hoping replacing the Fuel Pressure Regulator would fix it but it didn't. Any suggestions? Oh, & I connected the 2 wires going to the inertia switch. That was the 1st thing I tried. And I swapped relays. No help.