I used the following:
1 can seafoam in the tank; 1 can seafoam through the vacuum system- Flushed the oil afterward and put new oil and filter. Had about quarter tank of fuel and added about 1 gallon of denatured alcohol (you can buy at Home depot)
Emissions were virtually non-existant. (20 year old cat btw) Super strict CA emissions to boot!
good luck.