t25 siren noise?

[ISTOTOSAO]

My t25 has made a small police siren sound sincie I had all exhaust/turbo gaskets replaced. I installed joe p. mbc and 3 days later the noise got really loud and started having a rattle in the lower turbo rpms. I turned the boost back down and no change. Do you think my turbo is starting to go? it is has 3" dp back exhaust everything else is stock. another way to describe the noise would be to say it sounds like one of those whistles that are like a trumbone but a deep note. any help finding out what it is would be great.

p.s. are bolts on turbo are tight and I removed the heat shields to see if the rattle would stop. still there.

Thanks
Steven