I'm running a B16 turbo (no air filter on the intake unfortunately) and one night while driving about a 100mph on the freeway the turbine suddenly changed its sound to a higher pitch sound. It used to sound like uuuuuuuuu and it's like iiiiiiiiiiiiiiiiiii while at 10-20PSI.

What do you think happened? I checked the turbine, everything looks OK on the compressor part.

 

Have you looked at the blades on the compressor?

 

Ofcourse, A+ condition. I'm thinking that maybe something got in the intake and is at the entrance to my IC. Will check it out when weather gets better.

 

check for boost leaks