I am wondering what is the best set up for my car. in another topic in this forum someone asked what was better, piggy back or stand alone ECU systems. in a previous subject i was talking about faulty injector drivers in my 90 nissan maxima, would it be better to replace the Current ECU woth an aftermarket one and be dont with my injector problem? or would it be better to replace the stock computer then find a piggy back set up? this is a question that I am really wanting to find an answer for, and quite frankly, im tired of my car running rough.  

i would only pick up a stand alone if you are planning on changing and increasing your air flow signifficantly.  You will have a much easier time trying to get the car to perform and function like a stock car under normal driving conditions with your stock ecu  

any places you recommend? my ecu if faulty so i have to replace it anyway, the best price i could find was at jim wolfe and that was 250 bucks.  

you more than likely dont have to replace your ecu but reflash it instead, unless it is physicaly damaged... and while at it upgrading the ecu with a management system at the same time .. now if you 250 quote there is a management system ide say thats great considering i just dropped around a grand for my engine management (kpro) if you dont plan on modifying the motor extensively or in a way that could lean out the motor i would hold off for now and see about a reflash from a dealer.  

With the age of the car and the PCM, there could be internal damage due to moisture corrosion or just plain old simple... age. Corrosion in electrical components is more prevelent the older the unit gets. PCM issue are rare but they do happen. If you haven't checked connectors or ground contacts before you decided it was the pcm, you may find that some times the simplest things can cause run problems, like bad connections. No car is immune to this. You may need a PCM, but I would eliminate any other possibilties before condemning the PCM. Unless you had a pro look at it already. Just giving my two cents worth. I've been there with the electrical issues and found that 98% of all electrical issues, such as yours, are connector and ground related.
And as far as performance is concerned... get as much information about the products you plan on using as a piggy back or stand alone unit. Function and ease of use and installation your guiding factors. Not all products are equal, even though they have gotten extremely better over the years. VIVA COMPETITION! I would use a programmable piggy back unit, just for the ease of removing it if you plan on transplanting it to a new vehicle, in the future, with the same power plant. It's just a suggestion.