Replaced all 4 brake rotors with Power stop Z26 performance rotors. And also bled all 4 brake lines like hell and used DOT4 brake fluid instead of DOT3. Largely reduced the steering wheel shakes while braking, So now, I didn't have any steering wheel shaking while braking below 50mph. But steering wheel still shaking while braking over 50mph.
4) Replaced all 4 Brake calipers with Power stop performance Brake Calipers. Did not help with anything.
I am going to assume the brake pads were replaced as well even though it's not mentioned. It also sounds like you had done this work yourself? Did you happen to clean the hubs prior to installing the new rotors to have a clean mating surface? Also just because the rotors are new doesn't guarantee they are true. If they're not a premium brand they could have a little warp in them. Did you pull all the slides apart on the new calipers and use lithium grease to ensure free movement? Including greasing the tins that sit on the caliper brackets. To me if a front end part is bad enough to shake the front end above 50 mph it would be bad enough to shake it below that as well