I have aseries 1 VS with a T5 Borg Warner conversion in it. What would be a good suggestion with what I have, would you suggest buying a well tuned ecu or what would be good to run with the bigger injectors?

Are any engine lights coming on after the conversion? The reason I ask this question is that if you go with the larger injectors, then you would need a custom tune to suit. In saying this though, given your current mods, I wouldn't recommend going with larger injectors, just good standard ones are fine. If you were running standard injectors, then we would be able to supply you with a mail-order tune (along with other companies), which would offer genuine gains in performance and driveability.