P0120/ ECM test? Please Help!

At my wits end here. Keep getting this code. Changed TPS, cleaned MAF and throttle body, checked voltage at TPS and across ECM - all good, replaced battery terminals. According to the manual I used my ECM should be replaced but before I drop the money for that I was curious if there is anyway to test the ECM to be sure? Or are there any other cheaper leads I could look into before hand?

2000 tacoma, 4x4, 3.4L - s/c'd. Only mod is a K&N. The only other thing I can think of is the cam cover vent hose seems slightly too big for the nipple on the cam cover and could perhaps have a leak. From what I've gathered this won't make any difference though.

The truck runs near perfect although I don't have much base of comparison as it was very recently purchased. It has all of the symptoms of the superchargers (high gear ping, lean out, etc). The idle is steady most of the time, once it is warm it is a bit low and the motor will shudder. I have also noticed that (after wiping the code) it will usually, but not always, come on immediately after an episode where the idle will jump around (+/- 250) from 750 for a few moments.

I've had this truck for almost two weeks now and I'm starting to become very discouraged. I want to believe the seller didn't scam me with a busted truck because he himself had the emissions done.

Anything is helpful. Please and thank you!

Edit: Just to be more clear, TPS voltages were 5v power and .5v-3.5v signal without any hiccups. Is there a way to test the MAF?

 

Bump. Patched up the vent hose and ran a bottle of fuel system cleaner through it. Cleared the code. Ran it for 150 miles then got the code again. There doesn't seem to be any signs of it occurring. It was about 5 minutes after start-up. Going to check the harness for shorts or corrosion, maybe the wire is making intermittent contact with a ground somewhere. Also going to replace the PCV and grommet today.