at first it had a gas leak so we replaced the injectors and seals it got a spark plug and a boot kit it also got a intake gasket. when i went to bring it home from the shop it poured out sometihng white out of the ail pipe but then suddenly went away. now it idles rough between 1500 to 3000 rpm bouncing bck and forth constantly making as its lugging out the engine. anyone know why??? or what could be wrong?