is that pinging I can hear.....?

[TorpedoCreative]

Ive noticed that when I floor it i think I can hear what sounds like pinging? only really in 1st and 2nd (top of each gear). now I mentioned this to Subaru and they said that sometimes the car may ping if its under load (ie going uphill with a trailer) only this seems to occur without any load??
I always run premium fuel (mostly 98 )
The car is standard except a cat back exhaust and (a recently fitted) sprintbooster. btw I noticed the sound before I got the sprintbooster
Im not sure if the pinging is just more audible since the exhaust was done?
Does anyone else experience this?
Any ideas? apart from using an octane booster?

cheers

James

[sub108]

maby you have an exhaust leak block the end of the exhaust and see if you can hear anything

[TorpedoCreative]

its a bit of a late update, but I have established that the noise I can hear is actually only wastegate flutter.. ie the wastegate opening and shuting to control boost.. happens at high revs when giving it some