2004 Chevy Trailblazer

I had done a full tune up at 85,000 miles and at 90,000 miles I have a hesitation at idle. Once you are driving 20 miles and hour or more the hesitation goes away. I also have a slight admision smell and mis firing out of the tail pipe

Ac spark plugs?
How was the fuel filter?
Any check engine lights on or flashing?
Get it on a good engine capable scanner and read out data and check for codes.
Post back any codes.
Also run a good fuel pressure test on it.
Give us your fuel pressure readings.