I caution you on that large of an intercooler if you are keeping A/C. I have same car, same turbo, 2.5 x 5.5 x 27" I/C. The I/C fills the opening completely and blocks airflow to the radiator. The worst case is 100*F+ days running A/C at 45 mph, not even in boost. Sustained boost also will make engine run hot (no A/C). Hot means 230*F and rising. I have not yet done coolant re-route. Unfortunately, I don't have a recommendation on a smaller I/C, as it seems this size range is quite the norm. However, I can say that, at that boost level, a quality unit (can be had from eBay) in that size range is plenty enough, so I expect a smaller one would be OK.

Sixshoother has had similar issues with his NA, and has cut away some of the inner bumper. I thought I'd do similar, but not sure yet if that will help on the NB.

On fueling, what the guys said above.

EDIT: Doesn't look like there are smaller choices available, and you already have your I/C, so just be aware of the over-heating possiblity and the need to get some of the airflow to bypass the I/C.

I also had to move the intercooler back away from the bumper mouth to allow more air through it and around the intercooler. If you try to make it all go through the intercooler the car will overheat.

Yeah, if I had realized, I would have tried harder to relocate the A/C drier. That is what pushes the I/C forward into the mouth.

Would it be possible to fabricate some sort of air scoop to fit underneath the "mouth" that will push/re-route air up between the intercooler and radiator? I live in Phoenix so overheating would definitely be an issue. If no one has tried that solution I guess I could be the first to give it a try.

The first thing you need to know about the Miata's cooling system is that it's a defective design from the factory.

The engine in the Miata was originally designed for FWD applications, and as is common in most vehicles, had the thermostat on the flywheel-end of the head. When Mazda turned the engine 90° and installed it in the Miata, they moved the thermostat to the front of the head. This had the effect of allowing quite a lot of coolant to bypass the majority of the engine when the thermostat is open, and cooling performance suffered.

The common solution to this is what's popularly known as a rear-thermostat reroute, where the thermostat is moved back to the rear of the head where it belongs, the front outlet is blocked, and cumbersome plumbing is added accordingly. If you search the term "reroute" on this forum, you'll find plenty of information.

It's quite inexpensive to fix this problem using mostly off-the-shelf parts, but if you're lazy (and I assume you are), a number of off-the-shelf kits exist to help you, such as: Miata Coolant Reroute System This is the single best cooling upgrade you can do to a Miata.

Besides that, aluminum radiators are pretty cheap, and yes, you can buy a scoop of the sort you describe from Bell Engineering: BEGI Miata turbo Air scooper

With a rear-therm reroute however, you probably won't need it. I used to live in SoCal, and have driven from San Diego to Phoenix and back several times in summer in a turbocharged '92 Miata. So I'm not BSing you when I say that a rear-therm reroute, plus a cheap aluminum radiator, is all you need.