95 Geo Prizm, 127K miles, I discovered a small fuel injector leak, so I decided replace the O-rings, etc on all the injectors. While removing the intake plenum cover, this is what I discovered. I started to spray break cleaner, but I stopped to take these photos before I started cleaning. That is why u see liquid pooled up on the lower part. I stuffed paper towel in the intake to protect from debris falling in. There was some but minimal sludge in the corners and hard to reach areas on the lower part. Before cleaning pics After cleaning pics Brake did an OK job at cleaning but I found that Berrymans Chemtool worked better. I replaced the injector O-rings, etc, and buttoned everything back up. I took the car for a drive and no more injector leak for now. I would say that the car runs smoother after the intake plenum cleaning, but it's most likely in my head as it ran fine before. The car does not consume oil. I may go ahead and install a catch can. FYI, the PCV was replaced 1000 miles ago and the one was in OK shape as it still rattled.