Alright I read the other post and I can say that springs are easy to buy in a variety of different spring constants, free heights, solid heights, wire thicknesses, etc. I bought my springs for my subsea running tool from suhm spring and Smalley spring. I would just test my stock springs, call up suhm, and tell them my desired load at different locations and size requirements. They would probably recommend an off the shelf part number that would be cost effective....

The Metro XFi has one less piston ring than the garden variety Metros. Don't know about its valve spring stiffness, though...

If it were me, I'd keep the stock valve springs and install a low lift, low overlap, low RPM "economy" cam.