I was surprised at the number of people who had various and sundry fueling issues. A few suspect fuel pumps, a couple of fuel cells that could have been plumbed a little "cleaner", but I suspect quite a bit of vapor lock in many of these issues.
I've been out of the rally game for a while, but at least on BMW oilheads, a popular mod was to relocate fuel pumps and filters to external units. I have no idea if it was helpful, but at the very least they were more accessible to determine if those items were failing.
Also....free advice and for what it's worth; if you only need 12" of hose to run your aux tank to your main, and extra four inches isn't needed. With that, if your aux cell drains directly to your main tank and it is filtered in the main tank, a fuel filter in the aux tank MAY be an extra failure point. I saw this too yesterday. If you don't really need it, you don't need it.
FWIW and respectfully submitted.