For engines with fewer than about 100K miles or so or for higher mileage engines that have been well cared for, Berryman B-12 Chemtool Fuel Injector Cleaner (part #0116) is a good solution.  For particularly high mileage engines and engines with unknown maintenance history, Berryman Total Engine Tune-Up (part #0316) is the safer option of the two.  However, if you’re simply doing an engine flush immediately before changing the oil and filter, then Berryman Engine Oil Flush (part #1216) is an ideal product for that application.