It is sort of a wild guess what any problem might be from- I sometimes take a stab at what might typically be wrong and is easy to check, even if I could be completely wrong.
Maybe if my advice is way off, someone might kindly add a correction in a new post below mine. If you read a lot here you will see several calling me a moron, idiot, liberal, etc.
The factory service manual has several checklists to follow for troubleshooting that might help, and are more official coming from the factory engineers, instead of a backyard tinkerer like me.
Do you have Seafoam there? It was invented for cleaning 2-stroke boat motors in the 1930s, causing foam in the exhaust water.
“Banking institutions have banished precious metals and substituted a more fluctuating and unsafe medium; they have withdrawn capital from useful improvements and employments to nourish idleness for the few, who prefer demoralizing pursuits to labors useful to the whole; the peace of the whole is endangered by evils more easily to be deplored than remedied." by Thomas Jefferson,1810 (edited)