Where are you located? West coast fuel is crap so careful. TGV deletes allow slightly more air, so you OTS (crap map) won't work well with anything else. Run a stage 2 91 map and use 93, it may sound weird at first but think about it, it's looking for more air, so more fuel will be used. And yes, other than some tweaks the 15 wrx w/ FA20DIT is the same, just test at light load and slowly check your logs and gauges when tipping in more a bit at a time. If your DAM drops, you're doing something wrong.
Check out Cobb's infosheet about what to watch for and familiarize yourself with their product!