Because it is halfassed (cheap/low-bid) hardware clumsily driven by halfassed software/firmware that's too "dumb" to adapt to any substantial changes. I tried a bunch of mods on my '89 TBI 318 D100 and kept track of the results. The only one that helped a little(!) was swapping in a custom 21-psi fuel pressure regulator and a set of 3.9 V6 fuel injectors. The smaller injectors and higher fuel pressure (stock was 14 psi) improved fuel vapourisation and made the truck's driveability marginally better. There's not even an IAC valve; idle speed is regulated sloppily and slowly by a big honkin' external idle speed control motor pushing on the throttle lever.
Overall it's better than a carburetor in most ways, but that's about all that can be said to recommend it.
isnt it possible to get custome calibrations burnt for 88 89 factory mopar computers