I was thinking about removing my UIM and spraying throttle body cleaner in there to remove any carbon residue which has built up over the years. Would this damage it, as it is plastic? Can you reuse the gaskets? Would this improve performance a noticeable amount or is it unlikely to be any different? Thanks.
The intake is nylon-composite, so it should be fine with TB cleaner. Just don't try chlorinated brake cleaner on it. If you clean the runners, make sure the intake valves are closed before you spray and try to limit the amount of fluid used. You will have to turn the engine by hand to close the other valves and clean the other runners.
Cleaning the intake of carbon might improve throttle response and power a little bit, but it's not going to be anything earth shattering. You can probably reuse the gaskets, but I would put new ones on to be safe.