Posted by gmharris [72.219.148.98] on Friday, February 28, 2014 at 22:39:42 :
In Reply to: Re: I had to diagnose a loud noise one day. posted by gmharris [72.219.148.98] on Friday, February 28, 2014 at 21:38:44 :
And, I misread. "Back pressure" is caused by the exhaust not being able to leave the exhaust system as quickly as it is produced.
You are referring to "backing off" the throttle. And, I agree, it's probably a vacuum leak.