Heres a question........why did you replace the motor? What was wrong with the other that made you swap?
Aside from that... You said "......some of the sensors aren't plugged in.... looks like oil sensors or something..." If this is the case, it could be a temp sensor of some kind ( Im not to familiar with accords ) A bad temp signal to the air metering device can keep the car form hiting vTEC....If so,un-hook your battery ( make sure you have a security code if you still have your stock deck ) and plug those sensors in where they are supposed to go. BEFORE re-connecting the battery, turn your ignition to the ON posistion. Your gonna have a few minutes to wait so go make a sandwich and tell your girl to call me!!! j/k........come back about 15-20 minutes later. This should discharg the ECU's memory of that metering code and return it to it's " DEFAULT" mapps. Make sure everything is hooked up and installed EXCEPT THE BATTERY. TAKE THE KEY OUT OF THE IGNITION BEFORE YOU HOOK THE BATTERY BACK UP or you won't have a computer anymore...it will be a grilled cheese sandwich. You don't want this because you just ate a sandwich earlier. Re- connect the battery and start the car... don't touch anything in/on the car until it idles to normall temp. drive it for a little while then see if it will go into vTEC. This could fix it. If it still isn't driving passed 4,000, there should be 2 connections on your vTEC solenoid, one has one wire ( probally green, and in the top of the solenoid ), and another that has 2-3 wires in it. Check this one FIRST. Hopefully you have a volt meter, if not get one. Get a friend to help also. turn the car on and see if there is voltage between this connector ( if the car will run without it hooked up) ... if there is no voltage, listen to these guys becuase its probally a newer engine and needs a different ECU. If it does have voltage.... cut the car off and plug it back in and try the other one ( the ONE wire connector). Same test...except that friend has to rev the engine up to vTEC to send a signal through that wire. If there is no signal guess what.......no signal for vTEC. Check the wiring.......If the wires are good its an ECU problem ( either wrong ECU for that motor or it got fried during the swap )