Any chance you just got hold of a really poor tankful of fuel?
Have you pulled the plugs to check spark when the engine is warmed to symptom-producing level?
Anything more you can tell us about how/when it developed is all useful...
“THESE are the times that try men's souls. The summer soldier and the sunshine patriot will, in this crisis, shrink from the service of their country; but he that stands by it now, deserves the love and thanks of man and woman. Tyranny, like hell, is not easily conquered; yet we have this consolation with us, that the harder the conflict, the more glorious the triumph.” ~ Thomas Paine, 1776
1995 1500 Aspencade named "Cochise"
1985 1200 Aspencade named "Tatanka"
IDMWT club #18