is it possible to have a nos system on a car that has a turbo kit??  

Yes.  its possbile and actually quite common. (short answer) You just have to make sure you know your engine's limits and make sure its tuned correctly.

Engine Tuning  

how do you tune it correctly  

you need to buy an ecu (standalone)that will allow you to adjust your engine parameters like igntion timing, a/f and other features.  And then have it dyno tuned.  They will be able to build the correct ignition, a/f maps from scratch.  

where could i get a ecu and do you think someone in the houston area could hook it up and do everything for me thanks for the help man  

do i need to also buy a Turbo Timer or a boost controller let me know about the ecu too man  

Well to answer one of your questions, Yes there is a performance shop in houston its called Hennessy Performance you may have heard of them they make 1000hp Twin Turbo Vipers but they can tune anything or atleast refer you to someone who could tune your car. As far as the ECU goes it really depends on what your driving as to whats the best application however the AEM EMS, HKS F-Con V Pro, and Motec M800 are all great universal choices but always have a professional set your ECU up. But you'll need more then that. You'll need new pistons larger fuel injectors, fuel rail, fuel pressure regulator, fuel pump(s), cam gears, pulley, and most importantly a new cooling system because turbo+nitrous=HOT!!!!! So electric fans,radiator, oil cooling system larger intercooler preferably with an intercooler spray kit which if a nitrous set up that sprays on your intercooler to keep it cold because nitrous is very very cold naturally. So yeah your looking at some big money buddy so make an Appointment with a Bankruptcy lawyer cause you'll need on once your done.  

Oh yeah and about the boost controller and turbo timer I think I would just do that first. Get a boost controller if u need an example the gredd profec B is a cheap and affective one, any turbo timer is relativly cheap. Hell do the whole turbo set up. If your car has a stock turbo then just add a front mount intercooler, 3row would probably work, larger blow off valve like 38-42mm should do for a daily driver, new wastegate which is kind of expensive so is the intercooler but you won't regret the upgrades and then just go with a piggy back fuel system instead of a extremely expensive standalone. I recomend the greddy e-Manage it cost less than $300 and its effective or for just under $700 bucks you could get teh e-Manage Ultimate which is as close to a standalone system as you'll get with a piggy back plus its effective and cost efficent. plus some new fuel injectors wouldn't hurt I recomend 550cc/50-55lb to start with and maybe a new fuel pump which suprisingly aren't that expensive. Try that out first before you get nitrous cause nitrous may sound nice but unless your drag racing its pointless to have it and it will burn your pistons up in a heart beat.  

so i shouldn't even get nitrous?? i think i agree with you the only reason i want nos is to street race...would i really need to get all that stuff just to get nitrous?  

It depends on how much horsepower you want to make vs. how safe you want your car to be.  Of course your always gonna have your limitations.  

Don't forget to upgrade your internals before you run nos