Did you install a fuel return line to your tank when you put your new fuel pump on?
You should only use the latest manuals when working on your airplane so you have the latest information.
It might be a good idea to fly your airplane to a Rotax service center and have them look at it. The Rotax engine is a very good engine and only needs regular maintenance no more than any other engine.
The fact that you have to do MORE maintenance means the engine and airplane may have been neglected for a while and like anything that is neglected, it needs some freshening up!
You should look at taking a Rotax Service course also so you can do a lot of the maintenance things yourself! https://www.rotax-owner.com/en/education-5/rotax-training