electrical component on plenum 2000 3.8

Last week I did the 171/174 overhaul. Went fine. On the back of the plenum (firewall side) there was an electrical component which was white, with a dial of some sort on the top of it, located on the passenger side of the plenum. What is this thing? I don't have a picture unfortunately. 2nd thing. What does the dial at the top control? I don't think I bumped/twisted it but would like to know what to watch out for etc.

TIA

Piper

Last week I did the 171/174 overhaul. Went fine. On the back of the plenum (firewall side) there was an electrical component which was white, with a dial of some sort on the top of it, located on the passenger side of the plenum. What is this thing? I don't have a picture unfortunately. 2nd thing. What does the dial at the top control? I don't think I bumped/twisted it but would like to know what to watch out for etc.

TIA

Piper It's the EGR vacuum regulator. 1 block of 2 vac. hose is attached on it and 1 electrical connector. This device is controled by the PCM to send the correct amount of vaccum to the EGR according to the different condition of the engine (temperature, load, idle etc). The kind of dial that you have seen on the top is in fact a cover vent and if you remove it, you will find small foam filter under this cover.