A cheap way to de-carbon the engine is to get a spray bottle of water, and spray it into the throttle body with the engine running. This causes enough of a temperature change to cause the carbon to 'come off' for lack of a better term, of the engine parts. I haven't used this method, but am told it works. I watched a Tech at work decarbon a Mustang using one of those chemical treatments, the knock this car had before the treatment was horrible, it sounded like it was going to fall apart. After a few minutes of high-revving, and white smoke coming out the exhaust, the engine ran like new. No more knock, and it idled smoother. I would suggest either having the engine professionaly decarboned, (de-car-boned?) lol..or try the water mist method.
