Not really unusual to find these types of deposits in an engine that hasn't been cleaned, and probably used cheap gas for years. But this is a good opportunity to thoroughly clean your whole intake manifold and throttle body. Just be really careful not to mess up the MAF sensor. Unless you remove the heads, it won't be easy to clean the valve ports without sending a bunch of crap down into the cylinders, but it can be done. Might be better to do a light cleaning of the intake ports now, and run a few tanks of gas with a quality top-end cleaning agent after you get it all back together. The manifold and TB are by far the most important things to do at this point.