If I am running in top gear on the highway and ease into the gas to pass a car without down shifting, my waistegate makes a chattering sound. Any ideas. I thought at first the spring tension might be set wrong but I thought I would ask around first.

 

It might just be opening and closing a bit. I've had that before.

 

is there a cure for this ?

 

yes.. get on the gas harder and let her open up the whole way

if you have a boost controller it should stay shut until you reach max boost.. thats one solution....

second one is to reroute it into the exhaust so you dont hear it at all....

 

are you sure it's not detonation also?

 

Well, I can stand on the gas in top gear and it will still do it. As far as a boost controller I have a Profec B. I don't think it is detonation, but I cannot say I am 100% sure. The A/F is right on (verified on a Dyno with Gas Analyzer and with the Greddy A/F gauge that is installed). My timing could be off, but under steady state cruise the car runs good and at WOT running through the gears the car runs even better