Rough Idle Cant Figure It Out

[jairee]

I have a 1995 blazer. It has obdII on it but only has o2 sensors before the cat. the cat isnt on the truck and i replaced the one sensor that would sit right infront of it. I see there is one more on the header that I have taken out yet. It has a brand newly rebuilt engine in it with headers and dynomax exhaust. I was in Iraq when I had the engine and exhaust done so i didnt do it myself. I do know the plugs and wires are all new. the oil pressure is good sitting around 60psi. but it idles very rough and I cant get better than 14.8mpg on the highway. before I had everyting changed I was getting 21-22 on the highway. I cant see that it could be because the cat is not on there seeing as there are no sensors after the cat. I know it still could be the one on the header but it was good when it got taken out of the manifold and put in the header. I just dont have the money to be replacing 50-100 dollar parts that arent the problem. I have no check engine light or anything else on but I know its running very rich. Is there anyway I can lean it out on the injection pump or something along those lines myself? or where should I start looking?

[Nytemare]

I have a 1995 blazer. It has obdII on it but only has o2 sensors before the cat. the cat isnt on the truck and i replaced the one sensor that would sit right infront of it. I see there is one more on the header that I have taken out yet. It has a brand newly rebuilt engine in it with headers and dynomax exhaust. I was in Iraq when I had the engine and exhaust done so i didnt do it myself. I do know the plugs and wires are all new. the oil pressure is good sitting around 60psi. but it idles very rough and I cant get better than 14.8mpg on the highway. before I had everyting changed I was getting 21-22 on the highway. I cant see that it could be because the cat is not on there seeing as there are no sensors after the cat. I know it still could be the one on the header but it was good when it got taken out of the manifold and put in the header. I just dont have the money to be replacing 50-100 dollar parts that arent the problem. I have no check engine light or anything else on but I know its running very rich. Is there anyway I can lean it out on the injection pump or something along those lines myself? or where should I start looking?

Start by re-torquing your intake manifold...its probably dropping vacuum through the gaskets. you are supposed to re-torque the intake after 100 miles of driving.

If you had bad O2 sensors you would get a check engine light.

No light means sensors are working fine.