Why is my Ford Transit Custom struggling to accelerate?

I recently purchased a Ford Transit Custom and noticed that the acceleration is not as smooth as I expected. What could be causing this issue and how can I improve the acceleration?

It could be due to a clogged air filter or spark plugs. Try cleaning or replacing them to see if it improves the acceleration.

Another possible cause could be a faulty fuel pump or fuel injectors. Have these checked and replaced if necessary.