Hi John;
The 150 injector is a plug 'n play replacement for the stock 125 unit. It does flow a bit more and will be the perfect match for your 150 kit. The only issue is the stock ECU but in this case it will be fine. When running at less then full throttle the stock ECU will use the 02 sensor and correct for proper AFR and this will take into account the larger displacement. When running at full throttle the stock ECU will go into closed loop and just run off a pre-configured table.
If you want to get really picky, it's not perfect but it's darn near and it's very easy.
I ran it for a bit before selling it to a 125 rider in the UK. He loved it. On yours it will be the icing on the cake and much, much smarter then buying a bore kit that comes with the quasi-controller hack for $750 or so....
If you do it this way you'll have an inexpensive bore kit along with very good fuelling for very little money.
Now, if you'll excuse me, I'm just going out to do some Nitrous test runs
(I just love the sound of that) 