hesitation or stumble on first drive of day

have done a tuneup and even replaced upper intake gasket that I found torn at ports. coolant temp was low when I first aquired vehicle last august 07. Changed thermostat now mileage has dropped and it still has a stumble or hesitation when first driving vehicle until it warms up. Anyone that could suggest what I could check next would be appreciated.

What year and engine and mileage?
Any check engine lights?
Any codes?
Is the dist set right?
How is the fuel pressure?
How is tune up end?

Sounds kinda lean doesn't it, you might check the fuel pressure.
Here's where...

http://i131.photobucket.com/albums/p288/Clunk_/Image033.jpg