Where to source extractor headers for XK8 four litre V8?

Where can I get exractor headers for my 1998 XK8 four litre V8 and will they give a significant power boost ? I don’t mind if the V8 sound level is boosted at same time. All comments gratefully received.

Can’t say I have heard of extractors being produced for the AJ26 engine, may have to enquire about having a set custom made? I believe power can be release with a change/removal of mufflers

Thanks Robin. Looks like custom made will be necessary. My racing friends also tell me to “bar the cats” or replace them with straight pipe to improve gas flow. I’d do this except for RMS Registration requirements.

There are hi flow cats on the market but I suppose it depends on where you are.
Welcome to the site BTW its a pretty friendly group of listers