Hard to say. Last time I had something like that it was a lose bolt on my heatshield. No clue how. If you're not losing any power and it doesn't drive different, it has to be something like that.

Wait, DO YOU HAVE THE UPDATED FUEL PUMP RELAY?!?! If you do already then,

I'd troubleshoot in this order:

-rattle test not in gear @ same RPM
-check plugs
-check fuel filter
-check fuel pressure
-check all exhaust bolts
-kick tires
-push off cliff

If you go for the last option, remember to get your cell phone out of it, you're going to need a ride home

 

Are you sure it's not the BOV fluttering under low RPM? If you are cruising at about 2K RPMs you will get BOV flutter if yoiu attempt to give it gas. This is a common occurrence even with a tune. Try driving at about 3k RPMs when cruising.

 

well I am happy to report I think I solved the issue. Before even going through troubleshooting steps with motor running., I inspected everything and came across the only suspect from visual inspection. When I changed my sst fluid I had to remove the intake and just used a zip tie to hold it when I was done as the damn bolt on the back got lost on removal. It was actually very tight when installed. However, at this point there seemed to be some play from stretching and if I move it around I could get it to hit the hood prop, which is metal. Which could explain the metalic shudder sound. I bolted that sucker back down and haven't heard the noise since. I am guessing the higher rpm and air coming into the intake at higher speeds was lifting it up and causing the noise.

Thanks everyone for the suggestions. I was a little freaked out. Glad it was something simple and dumb

 

Good to hear, glad the fix was really cheap