Just bought a 90 Trooper 2.8
 

Hey guys just got a 90 trooper and it is open header I need an exhaust I replaced plugs wires air filter(dirty) and fuel filter. It had starting problems but not now it has no balls at all barely go california highway speed. Will being open header( cat and exhaust back is taken off) cause loss of power like I'm describing? Struggling going up hills and whatnot?