vtr/s conversion engine trying to cut out

[rozaladdd]

hi all just had my vts engine changed as it was dead, put a vts in there and it has been fine for about 100/200 miles then the temperature gauge went funny it just goes up and down ?

so i was driving today and the revs started to go down so i just left it and the engine cut out then, so i turned it over and it fired back up straight away but now it keeps trying to stall but not all the time any clues ?

my engine loom was crossed over from mk 2 vtr to a mk1 vts could it be the looms are or is it to do with maybe the sensors or coil pack, i have cleaned all the sensors on the throttle

Any help pleas would be great as this is my drive to work !