well I have a 1987 firebird formula it had junk shorty headers and I got longtubes now car runs like **** low idle and when I put it in a gear the car has a bad vibration and rpm goes to like 400 it revs good in park but if you drive it there is no power why its a tpi car with mass air p.s the car was fine with the shorty headers but they where old and had pin holes in them the car was fast and had a lot of power and im running no cats and one o2 sensor and I did have to cut it to make it longer I drove it on a open header and it pulled hard but after I put my o2 and mufflers on now running like **** no lights are on????????

 

ok just checked plugs and wires , cap and rotor they are good so what else should I look for its driving me crazy please help