Weird noise after installing headers

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!

Sound recording will be most helpful...

Spluttering could be backfire? Turbo Spooling I assume like air passing through an escaping hole?

Both different sounds...

Did you reuse the OEM gasket (on the head) ?
Wait until the engine is cold and try retightening the studs holding the header to the head. Light leak might be the issue

Yeah, like air passing through an escaping hole,
and yeah i did reuse the OEM exhaust manifold gasket fkk... i should have replaced it aye...

The studs were tight, forgot to mention it was like a tinny sound as well... and only heard when car is moving not when I accelerate at idle
but I took it back today (hume mufflers), he said it wasnt uncommon for stainless steel headers to do that tinny sound...
He also said the gaskets were in good condition and didnt need replacing,
soooo I am confusedddddddd is this normal for stainless still headers?!


cant really get a video as you cant hear it properly from my iphone
sorry if i sound like a nub..

I've come to the conclusion that it could be the slip joints... are you meant to weld them together? do you guys weld them ?

Because they're PLM, get TODA.

Pretty sure that air passing through a hole sound is from the hi flow cat.
That was what i was told and I noticed it right away with 2 of my aftermarket exhaust systems (one of them mugen twinloop) with the use of the cat.