engine cut out on hot day

[M & JJ Zvolanek <mzvolane@ozemail.com.au>]

Gday fellow audi owners
Since I added another relay for the fuel pump, that gets activated by the
original FP relay, I no longer (so far) had the engine die on me during a hot
day. Not with the full tank at least. 
I will keep my fingers crossed.
I got this advice from someone who's email I misplaced. So thanks a lot again.
If that person could let me know if he had any problems since then, I would be
greatfull.
What assumptions can I make if the problem was to reoccur with low level  of
fuel? Any thoughts on that would be appreciated.
Mark Z
'91 90 113k