Efi xr3i cam is the best standard cvh cam that ford did and worth between 3 and 5 bhp over the xr3i mfi cam.

Xr3i mfi cam is different to carb cam, less duration and sharper ramp angles.

Rs turbo cam is the same as xr3i mfi but with a different pulley as it has different timing requirements.

Efi cvh also had wasted valve stems to give extra power.

Not seen the different valve seats in all the heads i have looked at, maybe that was the rs1600i only?

Xr3i stayed hemi whilst the carb engine went lean burn. Hemi head flowed better and therefore helped give the extra 15bhp, well 10bhp, over the carb engine.

A lot of power was lost on the xr3i by retarding the ignition timing to 8degrees from the 12, this allowed it to run on normal unleaded without detonation. I run mine at12 and super unleaded as it feels flat as a fart otherwise.