IM gaskets are reusable more or less even if not new
clogged cats are normally an issue at 3K rpm and above. you indicated that it gets worse when you step on it -- hence the question.
fuel pressure regulator question was just my shooting in the dark, I doublt it's relevant, but def do what Keyser says:
Key off.
Release the fuel pressure.
Install fuel pressure tester.
Scan Tool connected.
Key on, engine off.
Run the fuel pump to obtain maximum fuel pressure.
Is fuel pressure between 35 and 40 psi (240-280 kPa)?
it will not affect front and rear different though, afaik.
now, since the injectors are behaving differently front and rear, inspect very carefully injector harness (i'm sure u did already though) insulation is known to crack, although on older engines, and it is known to rub too. doesn't look like an intemittent short, but who knows.
is it really smoking out of the exhaust pipe?
Actually let me copy from Ford manual:
Runs Rough/Misses/Buck/Jerk/Backfires/Hesitation
- Air/Vacuum
- Check vacuum lines for leaks, blockage or wear.
- Check air intake system.
- TP, IAT, MAF, IAC
Fuel
- Check for correct fuel pressure
- Check for fuel contamination/quality.
- Check fuel filter.
- Check for restricted fuel lines
Ignition
- Check for correct base timing
- Inspect spark plugs and plug wires.
- Inspect EI system for damage.
Power and Grounds
- Check for generator/regulator noise interference.
- Inspect electrical connections, wires, and harnesses.
Other
- Check engine coolant level.
- Check thermostat operation.
- Check EGR valve sticking.
- Check PCV valve for correct operation.
- Check for exhaust.
- Check for partially binding brakes.
- Check camshaft timing and cylinder compression.
- Check for weak or broken valve springs.
You pretty much covered 99% of it by now...
