prolly not wired up right...thats the #1 cause for no vtec and a swaped motor....especially running a diff obd.

hit the vtec solinoid with 12v and see if it clicks if it does, unplug the oil pressure switch and stick a paper clip in there to make the wires conenct, if that works you prolly dont have oil pressure. if it doesnt the ecu isnt sending it a signal. find the vtec engagement wire comming of the ecu and hook a test light up to it...let the car warm up and then get on it and see if the light comes on. if theres no light it could be tps, vss, temp sensor, or the wiring on anything that i have mentioned. good luck