The TVS on the output of the TIU is a much higher value than needed to protect the 244 signal driver chip, those TVS chips are 9V rating. Also, Adrian said what I've said about the TVS across the power supply when protecting the electronics in the engine. That's good, but having it right across the engine pickups in the engine and close to the actual electronics is simply better.
In the case of the TIU signal generators, I was looking at what could be done to make the protection boards more compact. I wonder if two back-to-back 8V Zener diodes and the 9V TVS would be a good solution. The exact Zener voltage could be "tuned" to balance the protection for the TVS so it doesn't have to absorb the power of a longer surge. The TVS will do the initial suppression, and if the spike lasts long enough, the Zener diodes carry the load. This would seem to be similar in concept to the diode arrays, but a far lower parts count. It might be possible to get the board size down to a very compact little board with a small enough parts count. I'm thinking about .3" x .5" or so. This kind of board could really sit right on top of the 244 chip and just solder directly to the leads. It would be easy to install, and there's tons of clearance on the top of the TIU circuit board.
