2000 S stumble at 4000rpm
 

I have a 2000 3.2S model. It's RHD UK model with around 70k miles. The UK model comes without primary cats. I have recently removed the secondary cats for a bit more sound. They were in decent condition. The car now resides in Cape Town, South Africa

The power hits VERY hard at 4k rpm and runs cleanly with no sign of misfire right through the rev range. I'm not actually sure if the transition should be quite so digital.

Last week I was cruising on the highway and eased the speed up in top gear. At 4k RPM on an uphill, she just stopped pulling. No amount of throttle would get it to increase, however a drop to 5th to break the 4k barrier and she took off nicely again. I've since played around revving slowly through 4k in lower gears and found 2 "dead" spots- at around 3850 and 4000. It seems almost like a total fuel or spark cut at those exact points in the tables. if you ease it into the "limit" then you're stuck there but if you hit it a little harder you slingshot through it and you're on your way again.

I've ordered an eBay Chinametric but it's not here yet, so I can't look at data.

The Chinese knock-off Durametric has such old copied software ,you may be disappointed/confused by the readings.
The first thing to check easily and conclusively on Durametric would be the Variocam function.
Or as the King suggests below ,tell us your MAF readings from Durametric.

maf probably. disconnect it and see if the problem goes away.