You probably don't remember my post "engine misfire" but you sounded like you know what your talking about so, here's my question. I couldn't afford a new spyder injection unit for my 97 gmc so I bought a used one just because I need this running. Any way, I was told the cylinders 4 and 8 are not firing so what would you change the whole unit or the injectors that go to 4 and 8. I didn't take my truck a part yet, (South Dakota is a little cold right now) but from the looks of things the injectors can be removed from the spyder unit. The used unit I bought is from a 99 with 120,000 miles and mine has 180,000. Also can this part I bought be cleaned up with carb cleaner without damaging it.