I have a 3.1 V6 Multi Port Fuel Injection . I have changed plugs and wires,and coil caps. Also put new fuel pump in it.Plus a whole new exhaust system From front to rear. The car has no power going up hills . Idles fine in park in neutral , when put in gear it hesitates. Also smell gas real bad when you first start it. I'm at my wits end. Don't know what to do next ,can somebody please help me.