hi i have a 3.2 xj6 1996 140k car has not been driven for a few months started car and drove for about 2 miles car started to run bad not take revs above 2000rpm and back firing through air breather starts ok and idles but when throttle pressed just not rev runs realy rough i have cleaned plugs checked wires and pipes disconected manifold to check if cat was blocked done diagnostic test no codes plugs were sooty when car is idiling strong smell of fuel would be greatfull if someone could shed some light on this problem i have also checked plugs on ecu all ok.