As Duncan said, start with a commercial option before going all hardcore on the engine.
I will usually use the Liqui-Molly Detox on any car i buy with the initial service, works a treat for me and then i use the standard flush at each service from there on but everyone has their own views on engine flushing;
http://www.supercheapauto.com.au/online-store/products/Liqui-Moly-Engine-Detox-Treatment-500mL.aspx?pid=156705#Description
If this doesn't work and you need anything more serious, you can move up the scale gradually but i'd leave diesel for the less advanced tractor engines.....
Jas