my blm reading is 108 and my maf is 7 - 8. everything was fine until i added headers & i also changed my plenum gaskets - any ideas?

 

Did you poison the O2 sensor with silicone?

 

no - i did not, but it is a new sensor. I remember reading in the past that weather plays a part in these readings, it was raining when i took them. Does that matter?

 

Rain only matters if the connection is bad. You were given false information. If it did matter that much, GM would have installed rain sensors.

Something else is wrong.

 

consider a heated O2,
headers are known for letting the O2 run cooler,
O2 has to be hot to be accurate

 

do most run a heated o2 with headers where can i purchase? I had to extend the o2 wire, would that make a difference? I also changed the plenum at the same time, can a vaccume leak cause this?

 

For the heated O2 sensor, get the AFS74 AC-Delco sensor, should be the one for like a 1995 pickup, Vette, etc. Have to get that from the dealer. Do not get the Bosch replacement sensor from a parts store, lots of folks have had problems with those. Almost everyone who has added headers has had to go to a 3 wire heated O2 sensor. Luckily, they're real easy to do.

If you changed the plenum, you could have a vacuum leak. Those usually (but not always) show up as a "hunting idle" symptom.

Hope this helps....

 

i used a bosch wheni swapped the headers - can that be the problem?

 

If it's a one wire sensor, you'll probably have troubles regardless of the brand with headers. Headers flow too quickly at idle to heat up a single wire sensor, plus the sensor is also usually located farther down the exhaust than with the factory manifolds, another reason the exhaust can be too cool for the sensor. The number escapes me, but the O2 sensor has to be at a minimum temp to work. The heated O2 3-wire sensor just has a built in heater to keep it warm enough. The 2 extra wires are power and ground for it's heater.