When I put TBI on my 87 Diplomat any time I got below half a tank it would suck air on hard turns or stops, killing the engine. Anywhere close to a quarter tanks and it was virtually undriveable.

I ended up going with a surge tank fed by the original mechanical fuel pump with the TBI return also plumbed into the surge tank with an over flow going back to the vehicle tank. This was back before all the fancy stuff they have today. That Holley Hydramat looks real interesting, even if it's pricey.