1995 Chevy Blazer hesitating at start up running

95 chevy blazer, during start up truck is running it sound like it going to cut off. Give it gas its fine. I can drive it, it drives fine. Was told in maybe the fuel injectors, cat converts clog, fuel filter or the fuel regulator. I replace the filter and the regulator and also the spark plugs cause gas was getting into the oil. What do u think it could be and what can I do or get to fix the problem