1990 Buick Century...Fuel or Air problem?

I have a 1990 Buick Century Custom. Once it hits a little hill the engine bogs down like its feeding for gas. While this problem is occuring there is very very little power getting to the engine. I changed the fuel filter and added some 'Heet' to my gas tank. Prolem fixed for a few hours until i hit an incline. Checked the Air filter and looks descent enough to not be the problem.

Maybe the Cadilidic Converter? Need help please.