[Vic55]

Steering straight doesnt necessarily mean your alignment is ok. You need to incorporate toe, camber, and caster. All measurements can be off even when lowered and your steering wheel is straight. Your steering can remain straight while the contact patch may have changed. Get the alignment as it appears you might be scrubbing which is toe problems.

I have the M550i springs- no issues except for a great stance and slightly more compression and rebound due to less travel. I drive my car daily over 100 mph in high speed bends no issues.