disco 2 TD5 cutting out

my brother has offered me his 2000 td5 as my 300 tdi has seen better days, all in all its a good motor, has the usual problems with rear chassis but he said he will weld it up before I buy, the only thing concerning me is that it cuts out between 3500 n 4000 rpm, it developed this fault when he fitted new clutch and flywheel and he says he's pretty sure its the crank sensor as he didn't disconnect it when fitting clutch n flywheel, it runs fine, starts fine just cuts out between those revs, id be alot happier if we could fix or identify this fault before I actually buy it,
any of you clever lot have any ideas/input on this problem??
thanking you ��

What are you doing at those revs with a Td5 though?... anyway you need to read some live data with tester cos at those revs it's possible that the MAF reading to exceed 650 then the ECM cuts fueling, especially if it's remapped, first unplug the MAF and drive it so to see if it cures it... beside that check for oil at the ECM red plug and if you find some replace the injector loom ASAP, the same if you find oil in the upper plug at the head

Not me revving it that high!! As stated it my brothers currently n I'm thinking of buying, further info from him os it doesn't do it all the tine just sometimes, when changing clutch n flywheel he forgot to disconnect the crank sensor n snapped the wire so he just crimped the wire together, when it cuts out he has to turn ignition completely off and then restart the engine which it does fine,