Will re-introducing a dump valve effect my map
 

My car has been (mostly mapped) with a dump valve delete, if I now add one will it effect the map, or will it need to be mapped again afterwards.

The car is jerky when cruising with lots of chattering on ever the slightest lift off, I think this may be down to the fact it doesnt have a dump valve.

I was just going to add one to see what happens but want to check first.

Just what ive done had no probs