The Physical parts are the same, they have changed their choice of connectors / tweaked wire length / connector placement on the '13 and again in '14 ('14 being the TPS, added a pigtail to avoid water intrusion). Cheapest route is to swap the '14 engine electronics for your '12's.
If you want to upgrade to the '14 harness look up Devilmanak on here or his E-bay store as he parts out brand new sleds. You should just need the main harness and the newer '13+ hood harness, IF the '14 engine was complete with electronics (IE; injectors, stator, throttle bodies / TPS, ECU, VR,.
Guessing $200-300 for the two harnesses depending on his current pricing.
The other difference is the fuel pump and hose connections; but from memory those changes are limited to the pump and pump end hose connections, I think the throttle body ends remain unchanged.