Okay so... hi I'm Justin 19 years old proud owner of a 2004 Mazda rx8 new to the forum

So I recently installed a new engine and transmission into my rx8 and by new I mean used, I heard the engine run and drive in the donor car, I installed it into mine, once everything hooked up/plugged in, I went to start it and it started revved up to about 2k rpm dropped to about 750 rpms, bounced up to keep itself alive then dropped to 0rpms and died, I messed with it for about a week realized the misfire in housing 1 bought a test light and figured out it was a coil, replaced the coil and it started right up drove it around the block a couple times shut it off it wouldnt start, messed with a couple things, MAF, PLUGS ECT got it to run and drive again, shut it off once more and now its going back to the idling problem any ideas??

notes- the connector on the EGR the goes to the air pump hose has a huge chunk taken out of it, would that matter?? maf screw holes on the air box are stripped so its just held in by the O ring, maybe need a new MAF and or AIR BOX?? I was told to clean the crank position sensor and pump the brakes 20 times with ignition on, going to try that today, any other suggestions??

Last NOTE, I took out the MAF and blew into it as hard as I could while someone started the car and it stayed on until I ran out of breath, does that sound like the MAF itself??? Or maybe a leak along the airbox somewhere