Make sure there are no fingerprints on the slide, take care with the diaphragm & align it correctly, check the jets for junk, paper towel the inside of the carb where the slide goes & make sure no paper stays in there, paper towel the slide, no fingers on it,
See how that goes,, if it still runs like crap, put the original exhaust back on. If it still runs like crap, walk away for a while. Think about what youve done in the carb, then, go back in,slowly, meticulously & scientifically, study everything in it, check float level if you messed with it,