I'll try to break this into pieces:
1. you can NOT unplug the MAP sensor (
viewtopic.php?f=5&t=54207) and run. You can unplug the MAF sensor to disable the EGR and run with a CEL set (NOTE there are free and $s tunes that will turn that CEL off).
2. might be easier to replace the MAP sensor than clean it. If you go the replace route get the BOSCH 0 281 002 845 or GM PN 55206797. It's much cheaper and works fine.
3. yes you can flash a DIY tune your self if you have the tune, the appropriate cable and a PC.
4. the GDE tune is pricey but it does a lot more good things than just turn a CEL off.
5. IMHO stay as far away as you can from any cheater or "programmable" live tuners. Most all of them just fool the ECU readings which can cause enough over boost to destroy a turbo.
6. FCV unplugged is ok but may cause a code. Some leave it plugged in but remove the internal butterfly which renders it non-functional. This comment will undoubtedly restart comments to the effect that the FCV is there to prevent a diesel runaway; it is not and it won't.
7. EHM is potentially very BAD as the end of the EHM hose can freeze in the winter which over pressures the crankcase which can blow the rear main seal. If you just "have" to keep oil from the CCV entering the intake like it does on every vehicle built after ca. 1969 then use a catch can with a relief valve like a Provent.
8. I know of no way to tell if you have a tune other than the GDE one. You can check GDE by emailing GDE your VIN and asking.