anyone ever modified an A/C?

so i've upgraded from a 250 watt to a 400 watt
problem is heat. heres my situation...
during the summer i ran a small window unit to keep the room the closet is in at 68, the closet ran at 78 with the 250watter
now i have a 400 watter in the closet and the temp is spiking up to 89...too hot!
the exhaust just vents into the room and im pulling cold air in from outside but the temps are still up, so now im running the ac to get the temps down to 75.
the real solution would be to buy a vortex fan or something thats better than my blower.but i cant afford that till sometime in january.
i think im gonna re run my venting to blow exhaust to the outside to see how that helps but im thinking it just might be better to rewire the thermostat to read the temps inside the closet with intake coming from that. anybody out there have experience rewiring a/c's?

you could use this, just mount it in your closet and it will kick on when you need it 2.no need to rewire just plug it in and its relatively cheap Ductstat Plug-In Line Voltage Thermostat - DS100 at The Home Depot

Don't you think that would make the rest of your house really cold? If I were you, I'd keep the thermostat where it is and just add more standalone fans to the closet until you can update your ventilation. You do need to get the temps down some, but 400s aren't too terrible to cool. Department stores are selling decent fans for ridiculously low prices right now, so you could probably find a few ways to cool things down without needing to rewire your whole A/C.

thanks for the replies
i think i've decided to cut a hole in the floor to use as intake, it will draw air in from the basement (which is cold but doesn't fluctuate as much as outside air) and that way i dont have a piece of ductwork running from an a/c into a closet.
if i get that thing that disrupt86 linked me to than i think my problems will be solved.
by the way i plugged back in my 250watter for the time being.