I have a 2001 Jaguar C type 2.5ltr petrol which I recently converted from automatic to manual...now it does not have power and it does not rev above 3000rpm and not go above 70kph....the gear changes are smooth

 

Sounds like your car is in limp mode. This could be totally unrelated to your transmission swap. I would have to guess that you also have a warning light on the dash. Simplest place to start would be to have the codes read and then search on here for the cause. Coudl be somethning as simple as a vacuum leak or could be something a little more involved.

 

Thank you very much, will look into it