AdamB

HI, I admittedly haven't read all the responses on this thread, but notice that you have a 1995 GT with equal length BBK headers right? So do I, but notice I have a tweecer to tune the EEC.

If you installed headers and God only knows what else mods without doing some sort of engine tuning, that is probably your problem. The 94-95 EEC's are touchy and need tuning.

With the addition of the headers, you are probably going lean... and could seriously hurt your engine.

I would suggest first and formost either buying a wideband O2, or at least having a dyno pull done with a wideband to check your air fuel ratios.

I would say your high mileage engine might be partly at fault, except that you say this only occurred after installing the headers...

ZiggyNamja

Thanks Adam - Actually the BBK were/are working great for the last 30K miles... no complaints there. I don't know if it is coincidental, but the problem started after the plug wires to 6 and 7 fried ON the BBK's...

I did the seafoam thing today - In the intake through the main vacuum hose (the big one downstream from the EGR valve, it works really well), the gas tank and the crankcase.
The intake reacted as everyone told me - lots of smoke, and that stuff really burns hot!. I repeated the process several times and I think that part is done.
The gas tank was almost full, so it will take a while for that part to complete and I am changing the oil tomorrow after putting about 80 miles of cleaning on the engine.
I re-installed the old O2 sensors for the cleaning, just in case...
I have to say that the top end is really good now, but the bucking is so bad that I should rename the car Bronco, rather than Mustang
Should I wait to change the plugs and O2 sensors until the gas tank has fresh fuel in it?

ZiggyNamja

Final Chapter
----------------------
So, after yesterday's seafoam fest the engine was running like crap, and I was quite doubtful that it would be ok after all that. Today, I proceeded putting the new O2 sensors back, fresh oil and new Bosch Platinums
Drumroll...
The engine runs AWSOME!
Low, mid and high range are on target, no bucking and plenty of tire shredding power.

This is my take on the original issue:
When the plug wires fried on 6 & 7, the erratic discharges must have affected the spark plugs as well as cause major carbon build up at the valves, resulting in the loss of power and erratic performance. Also, the excessive use use of octane boosters might have compromised the O2 sensors, further aggravting the situation.

The recommendations I received here were on target and I am grateful for all the help working through this issue. Additionaly, please note that if you are going to use seafoam on a heavily gunked engine, like mine, I have noticed the following:
- Seafoam burns very hot when shot into the intake
- It is helpful to put it into the intake at idle and then flood the engine until it stalls, let sit for about five (5) minute before cranking it up and blowing the heck out of the carbon deposits
- Use expandable plugs and O2 sensors. Mine were useless after the cleaning process and new ones must be installed.
- I only drove the car about 100 miles after using seafoam in the crankcase and then changed the oil and filter

Again, THANK YOU ALL!!!