Exhaust / Fuel Injection tuning

I am looking at replacing my original exhaust as it is slowly falling apart due to rust and previous owners dodgy fixes.
I am either going to replace with a DG 6 into 1 system or bypass and remove the original collector boxes and going straight to the original mufflers.
Is there issues with the fuel injection system ie tuning , rich, lean etc etc that I need to compensate for? I presume there will be changes in back pressure but not sure if it will cause any issues?
Thanks again

I'm not sure about fuel injection but I'm using the stock 110 main jets and they are working fine. I am having problems with the pilot jets being too lean.

The DG sounds awesome.

ok, may have to try it and see.
Thanks for the info.............cheers