1998 Chevy Suburban Stumbles when excellerating, especially uphill!!

[NYCHEVY OWNER]

1998 Chevy Suburban K1500 4x4 has recently given me lots of trouble when going uphill. I have replaced spark plugs as well as a catalytic converter, but I don't want to keep replacing parts and just hope for the cure...I was thinking fuel pressure is an issue but then it is only an issue going uphill sometimes.
Any help out there?

Thanks!