Yeah don't fool around with the IAT(intake air temperature) and MAF(mass air flow) sensors. I would go with UPREV Osiris Standard for 500 bucks. UPREV sends you the software and Cipher cable for datalogging that plugs into your OBD port under the steeringwheel/dash and they send you a baseline tune for your current modifications. Once you install the tune with a laptop via the Cipher cable and the emailed baseline tune, you proceed to do a few 0-60,0-100 and crusing runs while datalogging, then you send those logged runs via email back to UPREV and they will send you a custom licensed to your truck only tune for whatever octane fuel you use regularly. So for example you would receive a custom performance tune for 87 octane that will be safe and reliable. Also, when purchasing UPREV you get THREE E-Tunes, which are 3 more custom maps/datalogged runs that you make after installing new/additional performance parts such as headers... Check out UPREV's website and search the Titan Forums, you can't beat them.
Now, the option of a handheld programmer is fine for most people who have just a cold air intake and cat back exhaust. I personally would recommend the Superchips Cortex programmer. It comes with 3 Tunes to choose from which are 87,91,93 Performance maps. The difference between the programmer and UPREV is that programmers utilize the same ''generic'' tuning for each titan, the maps on the programmer are NOT custom calibrated to one's individual mods...However, the sole purpose I bought my old Superchips programmer before I got UPREV was due to the fact that it eliminates the WOT limiter, meaning that you have Full Throttle from a standstill while flooring it, instead of getting only 70-80%. This is due to Nissan's Torque management system and safety issues apparently.
If you don't plan on modding much more past a Cold air intake and basic cat back exhaust, i would say programmer which is around $100-150 cheaper than UPREV... BUT!!!! If you do plan on getting long tube headers, cams, etc...Go with UPREV and spend the extra coin and you will be able to Tune your titan after each mod.
I personally would recommend getting UPREV from the get go and getting a dyno tune through an authorized UPREV dealer near your location. The Dyno Tuner would give your Titan the UPREV Pro-Tune which is a dyno tuned one time ECU Reflash, which is what I have on my Titan and is the best route to go!