My truck has almost 70 thousand kms on it. 5.4lt auto. just starting off bringing
the rpm up to around 3 grand it kind of makes a blowoff noise that i never heard before. might do it 3 times real fast. its hard to explain. just curious as to what it is or if i should be concerned. any info would be appreciated.

 

Welcome to the forum

That doesn't sound normal. Not sure what it might be though. You might run it by a shop a see if a mechanic will go for a quick ride to see if they can identify the sound.