I think you need to change all 4 springs... at least I would think.
now the e90 and e92 springs are interchangeable.
My question is the i sport and regular i springs are different or no?
Also, I would assume changing to the i springs, i do not need to change shocks like if I added h&r sport springs.. I mean I can, but its not going to mess with the ride like h&rs would because its OEM, right?