95 Corolla 1.6L (4AFE engine) Previously I had a thread about a barely passing SMOG test due to high NOX and most suspect a stuck EGR. So I spend some effort taking out the EGR and its pipe (due to a stuck nut) together and found the inside to be very "free". There is a grey surface that I'm not sure if it is oxidation or just the material choice, but it wasn't wet or sticky. Parts cleaner seems to do nothing other than turn a bit brown/orange. However while look at everywhere for potential blockage, I notice that the intake manifold past the throttle butterfly is sticky. Should I go ahead and clean it with something? Will it help fuel economy?