I think next to EGR, this is a very neglected item. I pulled my solenoid off to test it just for kicks, and found it wasnt working too well. I hooked it up to a power supply here at work and blew through the barb. I found that the needle was sticking intermittently. I would turn it on, and blow through it. I would cycle it again, and now I couldnt blow through it. I would cycle it again, and I could blow through it. I would turn the power off again, and I could still blow through it. I poured a little air tool oil in both holes, blew it out with a blow gun, and cycled it rapidly. Eventually it was working like new again. Solenoids use an iron needle, which tends to rust a little over time and starts to stick, and it also wont seal properly against the seat. If its not the corrosion, the coil can start to become weak. I dont like the idea of the solenoid failing and dumping boost into the canister and the gas tank, among other little issues that can arise. I noticed that when I removed my gas filler cap, only rarely would it release pressure. Now its nice and consistent. I also replaced that little o-ring with a clover shaped o-ring that seals at 2 points instead of 1. I just happened to have some laying around here. I dont know why, but it improved my idle, and my BLM's changed a bit. If I remember right, they moved up. And the spread between idle BLM's and cruise BLM's reduced by about 3-5 counts. in the process, I noticed my check valves werent in great shape either. So between that and a sticking solenoid, I could have been causing damage to something.