A 255 was fitted to mine a few weeks back, the car ran better, more MPG with less pops and bangs on the over-run. The car will have been lean beforehand as I'd fitted a bigger TMIC and de-cat up-pipe so the pump may have made the car run richer, that said the 10yo pump will have been tired and the car did struggle to start when parked up-hill.

So non the wiser.

Would Torque Pro app be any use in checking the AFR/Emissions etc?

 

If the car actually had a catted up pipe previously then if you've removed that it needs a map.
You've got no guarantee it will run rich; in fact your comment on "more mpg" could suggest the car is now running lean. TMIC not so bad but removing cats without a map, especially one thats pre-turbo, isn't in my experience always a clever thing to do.