So just a quick note...

The cause turns out to be the headers - they had been dusted with some black VHT, but not ceramic coated. I figured it out when I started popping the bonnet open when parking after a run, and with no heat soaking going on, presto - the car magically started behaving itself.

My new $400.SU fuel pump (until it stopped working, they exchanged it for another, which works...so far) put out 2 psi, so it wasn't that.

My experience thus far, has taught me that yes, a lot of replacement parts are crap.

...what a shock!

 

The headers, so not the original cast iron manifolds from Jaguar ?

I have the original cast iron exhaust manifolds in my car where I had what was left of the ceramic coating sand blasted off.
They are now painted with VHT paint and give no problems with heat soak.

You have custom made headers on your car that was causing a heat soak problem that has been solved by getting rid of the headers ?

It's not quite clear to me what has solved the problem here.

EDIT:

Why not put the solution here, rather then starting another thread ?
I think this is where all this stemmed from.

Which fuel regulator for 3.8 MK2? - Page 2 - Jaguar Forums - Jaguar Enthusiasts Forum

 

Sorry, you are correct - I should've said stock manifold.


...and yes, it would have been smarter to continue on that thread - I mistakenly assumed people would connect my name with the issue.