I just had my emmisssions tested today and it passed on the high end and extremely failed on the idle test.
What should i replace, test, so my car passes the test. The car has a rough idle and trips up when just sitting in park.

Also my turbo is not fully engaging. When you press on the gas it acts like its building pressure in the turbo and you can hear it but it pops and backfires and doesnt accelerate. Sometimes it works fine but most of the time there is little or no acceleration. What should i check?