Volvo: Volvo 850, mass air flow sensor, mass air flow

Question
My volvo recently lost all power after 30mins of driving as the cat was broken so had it cut out and replaced, now the car drives better but still loses power at around 60mph and backfires. Any ideas?

Answer
Mathew,
Engine is low on power because compression is low, worn out. Low power due to old plugs, cap, rotor, wires, weak coil, clogged injectors. Blocked fuel filter, bad Mass air flow sensor, clogged air filter, broken air tube to manifold, low fuel pressure. Make sure the timing belt is lined up correctly. Rear portion of exhaust is clogged. Cat converter in not the right one.