Toyota: 01 Celica Cold Start Hesitation

My 01 Toyota Celica GT-S hesitates like crazy for the first 30 seconds
or so when I start up the car in the morning or if the car has been
sitting for a long time (like 8 hours or more). It only does this if I
step on the gas or drive it in gear for about 30 seconds or so after I
start the car, but not if I just start up the car and do nothing.
After about 30 seconds to a minute the car drives fine when stepping
on the gas. I took the car into the mechanic and he told me that
nothing was wrong with the car it after checking it out and hooking it
up to their diagnostics computer. Anyways, I have read several
postings that mention cleaning the MAF sensor, so I did this several
times (resetting the computer after each cleaning) and it has not made
a bit of difference. I cleaned the sensor with compressed air and was
very careful each time I cleaned it (I cleaned the two tiny wires and
the O2 sensor). I also still have the stock intake and stock air
filter on my car, so I am totally stumped. Could my MAF sensor just be
broken, but not showing up on the a diagnostics machine? I would think
that if it was broken that a check engine light would come on. Any
suggestions would be greatly appreciated. Thanks!