Well, I did exactly what you said...turned off water supply to boiler, set pressure to 15psi and let the boiler run for a little while and when i came back to check it it was at 25psi. So it sounds to me like it might be the coil that you mentioned. Now, how much am i looking at to fix or replace this part? and is it something i can do myself? Thanks!
Dunno, depends on how much you have to pay for the coil. Changing it can be a real bear.