Thanks! It ran shockingly well with no airbox and straight pipes. Easy starts, no stalls, no flat spots. Although if it was running lean that would help explain the overheating. I haven't checked the plugs yet.
I think it has to be said that the OP's experience with NO air filter and NO exhaust system beyond the primary pipes indicates that the concerns about pod filters are,shall we say, exaggerated. I know this is an injected system, but since it has no Mass Air Flow sensor, it must be a Speed Density style, where fuel is metered according to a fixed mapping of RPM, throttle position, air temperature, and air pressure. I have experience with these different types, because my '89 5.0 Mustang was the first year using a MAF system. The '87 and '88 5.0s used SD. The SDs required a different fuel map, meaning a reprogrammed ECU, to take advantage of any significant changes to the intake/exhaust system, let alone something like cam and related changes.
By contrast, my '89 with the MAF has had a larger MAF (70mm vs. 55mm), high-flow exhaust w/2.5" mandrel-bent pipe, high-flow cats, a K&N (gauze/mesh) high-flow air filter, and elimination of the intake baffle which was supposed to reduce intake noise, and it runs better than it did before any of these changes. It still has the factory low-restriction stainless steel exhaust headers. It has about 150K on it now, and runs better than it ever has.
Like the 1300 Kaw, the HO Mustang V8 is a torque monster, and because a MAF directly measures air density instead of inferring it, it compensated for all these improvements automatically and adjusted its fuel map accordingly. Not to mention that I now live at a 2700' elevation compared to 190'.
My point is, it seems the injected 1300s, like the carbed ones, apparently had a fuel map that was outrageously rich in order to compensate for the poor flow characteristics of the factory air box. When the intake and exhaust system are uncorked, the net fuel mixture ends up being so close to right on that it isn't even worth messing with the fuel map/jetting.
I had a conversation with one of the world's most experienced 1300 tuners, and he told me that fueling modifications were basically a waste of time. He has experience with all types and years of these bikes, and with all the time, energy, and money he has invested, I'm inclined to trust his opinion very highly.
I am about to get my '82 with 5600 miles on it into serious road use with minimal mufflers, pod filters, and stock carbs, so I promise I will report back with every positive or negative experience I have. Rejetting carbs per-se holds no terrors for me, since I've been doing it for decades. I have a jet kit, if it's needed, and I'm excited to dive into this new experience with CV carbs other than vacuum-secondary Holleys and Rochester QuadraJets.