Injectors?

Hi everybody,
I have a little question. Well, my car is a 2001 GT spyder and it's been giving me a lot of trouble. I had a misfire so the Mitsu Dealership said it needed a tune up=520$. No pb tune up is done but misfire still here. SO they .changed 2 O2 sensors =500$. Misfire still there. So they changed the computer of the car=1400$ (covered by Mitsu Warranty during 8 years..) but the Misfire is still here!?!?!? So today they told me it is probably one injector (estimated cost 1000$) .

So I need your opinion, Should I do it or do you have any ideas where the misfire could come from?

Thanks for your help.

if warrenty wil cover got fir it but $1000 for 1 injector isnt something I would pay. You can buy new injectors a set of 4 upgraded ones for my car for $400 give or take. granted it is a V6 and the injectors are prob. burried under the intake manifold.

If they changed the ECU before thinking of the injectors they sound like idiots to me. I dont think you change an ECU. Maybe I am wrong and that is how you are supposed to troubleshoot, but I mean a misfire can be cause by a VAC leak somewhere and be that simple