I was having a problem with rough idle, acceleration, and lack of power. Especially after the engine was up to operating temp. After going through the troubleshooting steps in the Haynes manual, I discovered a cracked vacuum line. Replacing the vacuum line fixed the problem, and she runs like a dream again.
I’m wondering what the part is that the vacuum line is connected to. I’ll try to describe the setup. The part is attached to the top, left (passenger) side of the engine just next to the two air intake tubes. The problem vacuum line comes out of the front of the intake between the two air intake tubes. The part has an electrical connector on top with two wires. The vacuum line from the intake goes into the bottom of the part. There’s another vacuum line going from the bottom of the part to a plastic “box” mounted down on the inside of the frame rail below the battery. The plastic “box” has another vacuum line going back toward the rear of the engine.
I got the following numbers off the “part”: E4TF-9C915-AA, J25 91B. I wasn’t able to tell from the Haynes manual what exactly this part is, or what it does. It’s obviously important. Any information would be greatly appreciated.

John

 

From what you describe, it sounds like the evaporative emissions system. It routes the vented fumes from the gas tank through the plastic box (the carbon canister) to the canister purge valve (the electric device) then to the engine to be burned off, rather than venting the fumes directly to the atmosphere.