Could be a dirty fuel filter, but it really sounds like a plugged cat. Mine seemed OK when cold and when cruising around town, but after warming up, the exhaust was extremely constricted and power dropped way off. (Especially at higher RPM) The only smell I could pick up was a mild 'hot/burning' smell which was from the extremely hot cat converter. Engine temp went up a little. If your car runs OK below 3500 RPM, it could be the IMRC stuck closed.
