it shakes pretty badly after you get to 3500-4000 RPM and sometimes it will backfire, Please help.
Clarification: What is the mileage?
It has 160k Miles
Did you scan it for codes and live data? (That's generally the first step in diagnosing a modern vehicle.)
Unfortunately those engines are known to have problems.
Oh and also what scan tool do you recommend?
It depends on your budget and what level of functionality you want. See the site scan tool recommendations in the FAQ.