VTEC in '91 Integra

A garage just put a used VTEC in my son's '91 Integra. Motor, trans, and computer. It only runs on two cylinders. What are the likely causes? Thanks

I have a '90 Honda Integra XSi, and I had this problem when I bought my car. there are majority of things that could be wrong.
1 the fuel sustem may need work
1 check the injectors
2 check to see if there's a leak between the fuel rail & injectors
2 these a faulty seal on the headgasket
3 your piston rings are shot
4 your camshaft is broken or worn down, could be from high compression valvesprings.
5 your ignition rotor, cap, wires, or plugs
these are just some Ideas, let me know the outcome.
Your V-8 can't touch this sweet Honda Integra XSi.....