High pitched whining noise at 30 mph and above

[Overdrive]

I occasionally hear a high pitched whininig that sounds like it's coming from behind my head in the engine bay. It increases/decreases with the engine speed. The alternator and belt have been replaced, as well as an IMS retrofit and RMS fix done. Other than that, and me changing an air filter and MAF, nothing else has been done in there, and the sound doesn't always occur, it happens some times and not others, and can come and go at random. Not sure why this happens.

I also get the other whistling noise from my passenger side while driving, but only somewhere between 60 and 80mph. Below that I get nothing and beyond that I think wind noise simply drowns it out, but that sound is much more consistent at those speeds, and I imagine it's the mirror or the bumper/hood gap culprits that members have mentioned before.