Hey guys i have a really bad problem. We got the car and first things first i did a normal tune up. Plugs,wires,cap,rotor,fuel filter, all the basics. Well about a month later i snagged off the exhaust. sounded great so i kept it that way wasn't loud just had a nice low rumble to it. Yes i also thought there wouldn't be enough back pressure but i checked and 4 cats is enough. Ok so about 3 months ago back in Nov. The car started having a really bad idle issue. It would almost die out then save it self and come back. This was of course after i changed the timing. Well so 2 days went by i tried idle relearn and that didn't help. Turned it back to 10 just like it was to start with. Well so i go back down a octane rating to 91. i was using 93 while on 14 deg timing. So the idle problem is still there. First things first i clean the MAF, IAC. After that didn't work i began to think i had a HAS problem. so i changed it. That didn't help. So next thing i did was run a bottle of sea foam through. Well that cleared out alot of crap. I did that 3 more times. Checked everything again. This time i thought the MAF was bad so i tried replacing it. Didn't work Tried replacng the IAC didn't work, Replaced the Dist all together didn't work. Ok so i am at a lose here. I pulled the plugs cleaned them put new wires on. All the stuff i am doing to the car has been Motorcraft stuff nothing cheap. i luckily had a connection at work and got 99 % of it free. I have had 3 different mechanics look at it. We checked all the TPS,IAC,MAF, all the voltage readings, O2 sensors, They were all functioning correctly. I mean 3 different people can't figure it out that were all Master ASE Techs and had been working on these type of fords for the majority of there career. So now i am at a lose for words. The car is pinging on 93 now. I hope that was just the gas i got. I usually use Shell and didn't so i hope thats the problem. The car will idle very irractically. It will even die out now on occasion. More then once or twice if i am not on the gas. I made sure the wires were run parrallel checked the plugs. I am going to go check the plug gap again today. My fuel pressure while at idle is at 30psi when i rev a split second it will jump to 40. I turn the car off it will hold 38psi in the fuel rail.