Im just wondering about what the differences between the 2 are mechanically. I have a 1.8 which ill be keeping for at least a year or 2 (until i can buy a RS) and at the moment is completely standard but i do want to modify it but i want to know if some engine upgrades would be transferable between the 2 for example a cold air intake, cat back exhaust etc.

Also ive kinda noticed a general theme. Is the engine its self not very tunable as the reason id like to be able to swap them is they're seems to more power difference from the RS engine when upgraded from what ive read so wouildnt mind spending the money now and not getting massive advantages if i could later on.

If ive been unclear please ask me too explain
Cheers