My car is losing power or bogging down once it is heated up .

Remove the spark plugs and keep them in order of the cylinder s they came out of.See if any are 'cleaner', or noticeably different from the others. Reply with results of that inspection. Another thing, would be a cooling system pressure test. Half hour or more, given your description. Any check engine light? Any other symptoms? Maybe 'create' an exhaust 'leak' between the converter and engine manifold, IF the exhaust is restricted (converter), then this may be an easy way to help isolate that and verify, as needed. Reply with results.