well let's see now: bike has been modded....ecm mapping modded....exhaust modded.....you "saw" that the mapping is modded. long story short you have absolutely no base-line to determine what the potential problem might be. i can assure you that your XB "spat and sputtered" long before you bought it 2 months ago and may very well be the reason the PO sold it. establish some sort of base-line. from that you'll quickly determine if the motor is sound internally or not....if an electrical problem exists....if a component problem exists...if a grounding problem exists.
a base-line in your case is: a known good ecm with a tune specific to your exhaust system and air filter; fresh set of NGK DCPR9EIX spark plugs; fresh set of plug wires; every single ground is removed, cleaned, reinstalled including both battery cables to terminals; and lastly confirm that every single item from the air-box base plate to the wiring underneath same and the TB intake horn is intact and installed correctly and no unplugged sensors such as the IAT sensor. lastly and most importantly, any and all ECM fault codes causing ECM to illuminate MUST be cleared.
if the above beyond your skill level seek out someone who can perform these simple tasks, tell them what you need, and go from there. you may very likely have something as simple as an unplugged IAT sensor...a TPS sensor that needs reset....or a lazy O2 sensor. you can't ascertain any of that until you follow my recommended steps above.