Although that sounds more like an air leak, you can verify or eliminate the slide as the problem by removing the air cleaner and looking down the throat of the carburetor while working the throttle grip. Use a mirror if necessary. See if it is in fact getting held up in the slide bore of the carburetor. Usually if this happens though, the engine will just scream at full throttle or close to it.
This is just step one in the diagnosis. Check it out and get back with us, ok?
You could take some material of the outside diameter of the intake manifold and if its really that tight you can also ream out the carburetor...but just a little and do it carefully. Clean everything well after you do any sanding or grinding.My problem when installing the carb was the carb was very tight sliding on to the manifold. I dont even think I was able to get on all the way to the stop. It went on barley past the slits cut into carb where the clamp goes on. Think I can sand down the manifold tube??