Hey guys

I just had my headers installed on my dc2r they were PLM TRI Y standard tubes and also got a flex,hi flow cat with it, all were new. However after driving for a bit I noticed a weird sound when I accelerate at almost full throttle and mostly around 4k rpms. It sounds like a splutter.. almost like a turbo spooling... Just wondering if this is normal ? or has anyone else experienced this and what was it ? Everything seems to be fine just this weird noise...
I also have a resonator and mugen twin loop if that helps.

any help will be appreciated, thanks!