Hi, I really need some help. I installed a new pressure tank which was preset at 28lbs and the cut in for the well is 28lbs as well. The problem is the basement is getting a lot of water pressure but the main floor is not. What do I do now? Please help I'm very confused! Thanks Sam

Two things:

1. The pressure in your tank should be set to 2# BELOW the cut in pressure for the pump. So, for instance, if the pump cuts on at 28# (yours), then the tank pressure would be set to 26#. This is done with the system off and the tank pressure drained to zero by opening a low level cold water faucet. Add or remove air from the air valve at the top of the tank until you get what is needed.
2. In your case, the tank pressure is not your problem. You would expect the second floor to get marginally less pressure than the first floor, but not by much and not very noticeable. I am assuming this problem was not there before you installed the new tank. If that is the case, then I'd check the aerators on the faucets. Probably got clogged up when you changed the tank.
3. Do you have a filter or softener on your system? If so, try bypassing it and see if that improves things.

the basement is getting a lot of water pressure but the main floor is not.
Jlisembe gave you good advice. The problem's not in the bladder tank setting, but in your supply line to upstairs. Is there a valve in the line going upstairs? Back to you, Tom