Wacky Suabaru diagnostic help needed

02 Impreza 2.5(NA) TS, 5 speed, car was running rough, bucking, low power, missing at speed, low lumpy idle, etc. Tested fuel pressure(tapped right after filter), 35 psi running, should be north of 44.5(regulator pressure) wouldnt prime in the speced range(65-100 IIRC), needle would jump into the 40s when the throttle was blipped, so I figure the regulator is OK.

Replaced fuel pump(denso), still runs like crap.

Replaced coilpack, duralast, turned out to be a reboxed made in Japan Diamond brand, OEM, so it should be good.

Now the car is driveable, but still roughens up quit a bit intermittently after warming up a few miles. I thought igniter, but it turns out that's part of the coilpack.

Plugs were replaced 2 months ago, wires are under 40k miles old. Fuel filter has less than a year on it.

We deadheaded it after replacing the fuel pump, and the coilpack.

No codes.

Thoughts?

Edit: update: Replaced IAT/MAP with a used one on the shelf, no change. Will try unhooking ECT sensor tomorrow, I can't find my ELM327 reader, and am only working with a code reader, so sensors diag is a bit of shooting in the dark.

Bueller?

We drove it some more today, heavy surging, seems to clean up past 3krpm, it runs fine at all RPM if you keep it loaded or coast(no cruising) which leads me to think EGR. However, I can not locate a EGR valve to unplug.

Using the unplug sensors till it runs right method, it would appear the front O2 E36 M3 the bed, presumably due to the rough running from the low fuel pressure and bad coil.

Check fuel pump electric circuit for voltage drop and bad grounds.

In reply to Kenny_McCormic:

Sounds like things are well on the way. When the engine starts running better at about 3k rpm that is a big clue that the o2 is bad because that's where the ecu transitions from closed loop to open loop fueling.

Soooo, take it out today or are you gonna soak it tonight and do tomorrow? Thank goodness access isn't bad for that o2.

In reply to Ojala:

I think we're gonna go with the do a few WOT pulls around the block (w/ sensor unplugged) and then get it in the air quick before it cools down. Gotta go to advance to pick up the new one and rent a socket anyhow.

Sounds like a plan, here's to hoping it stays hot till you can get the wheel off and pop the clips on the access panel.

If you run out of options, I would check the timing belt marks & do a compression test. I've had valves go bad and the lower compression caused it to really run poorly.