1995 blazer emmission control?

I just bought a 1995 chevy blazer 4.3 vortech 4door 4wheel drive,3 DAYS AGO.
well i took it and had a code ran on it and it came up as aux emmission control. ???
Does anyone know what that is?
The cheack engine light came on and went back off.
And it is missing during idel sometimes its fine and sometimes its not.
and you can smell the fuel burning rich.And have very low gas mileage
PLEASE CAN ANYONE HELP.PLEASE

Unsure of your code, might advise the code number, but... The poor gas mileage and smell are possible indicators of CPI failure. A lot of information on here if you search. The fuel pressure regulator and injectors sit under your intake plenum. The regulators are prone to leaks which will cause anything from missing to locked up engines due to cylinders being full of gas. You can remove the round sensor under your vortec plate and look inside the plenum for bright shiny areas. The entire area inside should be dark. May have to rmove the entire plenum to be sure(I am going to be doing this to my 93 in about 4 days), but that is best place to start. Other problems with these, EGR valves with carbon on them, vacuum leaks, dirty idle air controls. Plenty of information here, use search and check out the "important" topics listed above.

try removing and cleaning your EGR valve.

What is a cpi?

What is a cpi?

First of all , what code number was it.

They have to supply the number.

I looked up all the codes and don't see a code for that fault.

What is a cpi?

Central Port Injection... Basically it's your fuel injector. What happenes is that the regulator starts to leak and dump gas. This can cause a rich fuel condition and send your emissions controls and output off the chart.

Pull your upper plenum, check for washing (where one side is cleaner than the other) If your passenger side is washed, it's your CPI, if the driver's side is washed, it's your nut kit.

Should either of those be the case, replace them, then do an oil change to get any gasoline out of your oil.

What is a cpi?
There's some info about it here: (basically the long version of what rlith just said)
http://www.automotiveforums.com/vbulletin/showthread.php?t=462726