Replaced intake manifold and thermostat and still no heat

What is your question?

2003 Mercury Sable, not heating. the a/c must be disconnected when attempting to use heater otherwise the air conditioner will kick on while using defrost. replaced intake manifold and thermostat, and now it’s beginning to “be chugging” while driving. Smells sweet at times

How long has your 2003 Mercury Sable had this problem?

2 weeks just got back from repair shop