Engine power problems

I recently got a 96 4cylinder xtracab tacoma and I bought it knowing it had power issues going up hill and after shifting into 3rd gear. It also had an intense sputter when going/starting on a hill. The previous owner brought it to the local garages and no one could figure out the problem. So my dad figured if we just swopped the engine we'd be fine. We did and had the same problems. We changed the fuel filter, alternator, oil, and battery same problems. If anyone else has had the same problem please let me know because i've dumped plenty of time and money on this guy and cant stand losing. Im into any suggestions at this point.

 

Ngk or denso spark plugs? Ngk wires? Denso o2 sensor? Does it have an egr valve? Tps sensor?