the revving could be because of an air leak from the throttle body gasket so its worth replacing that as a starting point. it could also be linked to the speedo dieing which is a very common fault and does produce both those symptoms. the cause is the vss (vehicle speed sensor) which will be on the gear box somewhere, just check your haynes.

as said the gasket is first to try as thats wht you've disturbed recently but next should definately be the vss.

btw the crap on the throttle is there from new, you didn't need to clean it off.