starting problem

[1meanz]

car will run perfect, and start almost every time. but every now and again, when at op. temp, when the temp outside is below 10 or so, it will not start. will crank and crank and crank and try to hit, but wont start. i can put my hand over the tb and itll crank right up, i can even rap my hands around the cone filter (just a cheepo on the maf sencor) and itll start right up no problem and run and crank fine for a wile then the same thing. any ideas guys? done the same thing with all the stock box and ram air stuff so it aint the filter. and its hard to cover the tb and crank it at the same time lol. dont always have someone around.

btw, 2000 grand am gt 3400