My car has the standard fuel pump on it at 120,000 miles I'm thinking I might swap in the walbro 255 I have sitting in my garage just to be safe.

If I do this will I need to get my map adjusted?

Car is a 1.8 turbo with megasquirt and 550cc injectors.

 

possibly. the base pressure on your fuel rail will increase so you may just need to lower your req_fuel ever so slightly.

 

Ok I'll see if I can get hold of my mapper and ask him.

 

I'd expect the base pressure to increase at idle, but not at higher RPM. A retune may be required, IMO.

 

If you can run a proper regulator and set it for the stock base pressure you wont need a re-tune at all. I wouldnt run the wally 255 on the stock regulator. Too many people complain of fluctuating fuel pressure at idle.