I would contact the seller for more details. It sounds like a well sorted machine. Carl is a carb guy (which is a good thing) thus his reticence for a car with fuel injection, particularly one that has a aftermarket set up. I would bet it is Mega/Microsquirt which means it should be reliable and pretty easy to deal with. Get some sense of what sensors he used, most people who do this likely can produce a spreadsheet of parts and so on that were used in the build. This makes it easy to service later. If it is as I have described I would feel pretty good about it but I am pretty computer savvy and intend to do this to one of my X’s.
One could do as Carl would do, which is pull that stuff off and put on a nice single or preferably dual carbs. This would make it a pretty hot build car and likely something most backyard mechanics could deal with who are not computer nerds
Personally the things that are most important about buying an X is that the body is in good condition, has the least rust possible and that the various electrical systems work properly. For me all the mechanicals can be fixed pretty easily. Fixing rust and electrical items are either a nightmare or just a pain in the ass. This car looks to be well sorted by someone who really cared. It also has all the goodies many here spend years acquiring and installing.
I would see this as a car worth strongly considering if it isn’t rusty and things work.