im going from the stock 550cc injectors to 720 and 1600 CC injectors and a walbro fuel pump now my question is after i change the injectors and the fuelpump will the stock FPR work and will i have to re adjust my fuel map on my ecu.

 

Stock Fpr Should be changed and yes the ecu will have to be hacked/replaced

 

I already have a standalone ecu but will my tunning be alot diffrent from what i have now

 

yep

 

To rough in the tune you can approximate the on time by looking at the injector size. Assuming you keep the rail pressure the same you'll have about 25% more capacity on just the primaries and 100% more capacity on the combined primary and secondary injectors. Again, assuming rail pressure is unchanged from the previous setup you should be able to take out 25% from the primary map and halve the secondary map. It's easy to go through the 2D maps, on a Haltech anyway, and make changes by percentage. For safey sake leave yourself a margin of error. At this point you'll need to do the actual tuning but you should be in the ballpark.