What is the rattling noise in engine bay

What is your question?

'07 trailblazer LS . When I am at idle at a light or even slowing down the engine makes a rattling noise .

What makes this problem better or worse?

When I put slight pressure on the gas and the tach goes up barely it subsides.

How long has your 2007 Chevrolet Trailblazer had this problem?

2weeks.