I have used Berrymans Carb and Injector Cleaner for several years; 1 can for each 16 gallon fill up on my previous 116 450 and now my 126 420; after regular use I have the cleanest fuel distributor and valves with no carbon residue at all plus you get smoother engine running and a bit higher fuel octane that makes the car run smoother and have more pep. Found at auto parts stores for $2.68 a can; I even seen it at 7-11's.
K.J.