Problem under full throttle

Well, after transforming the Williams, I have a problem that I tried fixing now for a while.

I changed the engine for an younger one with less miles on it and K-Tec head, Piper cams and adjustable pulleys. Since this, when I try to put the throttle down, it feels like running into fuel-cut...
I checked the cam setting, the Sparks, the wires, the injectors, the TPS, the throttle body, the Ecu, and the fuel Pressure regulator and nothing seems wrong. The car drives OK when you rev it slowly, but if you step on the gas, it does not work.

Anyone got an idea that did not come to my mind?

When you say checked the TPS, did you use a multimeter to measure the readings it's giving? Is it only doing it when driving, will it rev fully when stationary? Possible lambda fault (pure guess that is tbh)
Is it idling correctly?

Had a similar issue on mine many years ago, wouldn't go over 110mph at all, it ended up being a poor connection on 1 of the injector plugs

Could be the map on the ecu? Does this fault appear at certain revs, could be a flat spot in the map on the ecu?
Has the engine been mapped/chipped for the mods on the engine?

I took the car to a local Renault Dealer and they connected the Diagnostics (XR 25, I think it's called). It wrote no fault, except a temperature sensor. Yes, only when driving, it even revs to 6500 rpm, just cuts out when giving full throttle.
Idling is ok, a little lumpy due to the Cams, but stable.

The diagnostics should have found a faulty lamda? And the connections seem ok too.

I tried three different Ecu's. 2 originals and one Cup Ecu. The engine is not been especially mapped, but should work with the original Ecu?

Thanks for your ideas so far!

The map could be your problem then, if you've changed the cams then the engine will require more air and fuel than a standard set of cams as the valves stay open long etc.