2002 Grand Am 3.4L automatic 48K- 2 weeks ago I had to replace intake manifold gasket and cooling fan motor. Also had fuel filter changed and changed the oil.The car now idles high and using excessive about of fuel. The car was scanned and no codes.Normally I would get 320-360 miles per tank ( before repairs were done )The last 2 fill ups only 200-220 miles per tank.The exhaust smells stronger, not different, just stronger. Any idea what the problem could be? Thank you