Is anybody aware of any in-tank fuel pump replacements that outperform the stock ones? I would prefer quiet, if that's possible. Thanks

 

I can't picture how the connections are made inside the Jaguar's tank (I've never changed a pump in a Jag), but in another highly modified application, I used a pump specified for the Toyota Supra mk4 twin turbo. Lots of those cars are set up for well north of 500hp, its quiet and Toyota quality. It's connected with a simple 5/16" hose barb. Just make sure whatever pump you use, that if you have to install new rubber hose inside the tank, to get fuel hose rated SAE 30R10 as that is the specification for hose that is intended to be submerged in ethanol fuels.

 

Bosch 044 and Walbro 255. I have 2xWalbro. Just make sure that they are genuine Walbros.
If you need just very quiet pumps, you may try some others. The high flow pumps can be very loud ones.

 

By all accounts the Supra MkIV pump is a great pump, and especially the modifed pump.

Both the MkIII and MkIV pumps are Denso. My MkIII pump was still going strong at 21 years of age when the car was sold.

 

I've had a bad expirience with walbro fuel pumps.
Bought one from rockauto for a Chevy Caprice i used to drive - the pump had failed two weeks later.

 

Yes, I have read that there were lots of cheap Chinese knock-offs of the Walbro pumps that flooded the market and that even many of the internet vendors don't know that their stock is counterfeit. I personally know someone who had a brand new Walbro pump fail (I was in the car with him when it went out) and suspected he got a fake. I don't know how likely it is, but I also don't think Walbro fits your criteria of "quiet" either.