If you downsized your pump then the new pump could take a little longer to get rid of all of the air in the pump basket. However, any size pump should be able to purge all of the air in the pump basket at full speed in a reasonable amount of time.

However, if the air never goes away, then you could have a small air leak on the suction side of the pump. Usually this occurs on the pump lid seal but can also occur in the drain plugs or even valves. Given you probably changed some of the plumbing as well, it could be in those sections.

A few more questions might help:

What is your old and new pump model/size?

Are you running at low speed?

What was and now is your filter pressure?

What other plumbing was changed?