Use lightweight rims.actually there's damn a lot of things you can do to improve fc.
1. Reduce overall engine load like what Gunnerz suggested. Aircon compressor kick. Check that your grounding is all good. etc.
2. Lighten your car interior, remove heavy-ass subwoofers and spare tyres (replace with patch kit) and skip all the downforce mods.
3. Fuel filter, ignition, fueling, air-intake - all these need to be in optimum condition.
4. Spark - some say that bigger spark will help. I personally don't really know. Kits like those that increase spark help make things run smoother. Back then with my wira I tested and share in ZTH this spark plug cable that increased the spark and that seemed to work wonders with my power which indirectly helped my FC.
5. Put a brick behind the accel pedal. Driving smoothly and non aggressively improves FC and keep revs below 3k rpm. You want FC you gotta live with the boring.