Need some ideas!

[trueExplorer]

Hello, I am in a bit of a jam; my x is due for emissions and just a week ago-it started giving me trouble. First the check engine light came on-b2 s1 slow response, no big deal, i threw a new one in, cleared code. Almost the next day, i heard what sounded like a mis when it started (cold) that would go away about 20 seconds later...But when I started driving, it would mis or bog or stutter horribly only under load, and this is also only when it was cold. From a stop, it doesnt do this, nor at idle-only when im already going about 25 mph or more. Then, i got another CEL with the same b2s1 slow response, b1s2 heater fault, b1s2 lack of switch indicates lean-and i just changed b2s1 week earlier! I cant get the after cat sensor out now! I tried everything, heated it up, pipe on the end of the wrench for torque-nothing, it wont budge! But if anyone has any idea about the mis,bog,stutter when cold and under load (and i mean the slightest acceleration, i dont dare give it much when its already doing this from barely any gas). I have no misfire, injector, MAF, ECT, codes nor rich or lean codes (except from the after cat which has a heater fault also). I checked the voltage for the engine coolant temp sensor thinking if it was faulty the computer wont intitially start and run it rich until warm-up, but volts were right on, and the temp...
I love my x and im willing to fix whatever it is myself, i just cant afford to have a deal or shop do the work for me-im fairly mechanically inclined and my bro is a diesel mech with every tool in the book...He thinks i might have a wiring issue for the b2s1 code, but really doesnt knwo what the mis/stuttering thing is, his best guess right now is a manifold gasket, but since i have no lean codes, it doesnt seem right...Please any ideas at all would be greatly appreciated! oh yea, 97 4x4, OHV 4.0L, with brown coolant is the res, yikes!