hello chevy ,,

i have got chevy caprice 08 ... IN US called pontiac G8

engine : LS2

i just install ( HEADERS ) /// Afe FILTER // LAST 2 MAGNAFLOW MUFFLER .160 SLP thermostate , BASIC TUNE ,

also i remove the catylics converter .

now the car in perfect condition but my major problem is the strong smell in the exhaust . not inside the car only outside , that when i want to put anything in trunk i feel the smell strong ,

there is any solution to decrease the carbon smell ?

Yes, install catalytic converters.

From what I understand, the smell is worse the richer the car is running (cold start).

The smell is all the time. so u advice me to put the stock cat ? Or magnaflow cat

Any catalytic converter will cut or completely eliminate the smell. If you are concerned with performance, a high flow unit would likely be preferable, and better than no catalytic converter.

I have a high flow unit, and still have the smell when cold, but it goes away quickly as the car warms up.

If you have dual exhaust, you will likely want 2 catalytic converters, one for each side.

If only in colds ,, of course i need them .

My Q: could i put the cat now with headers ?

I have the stock cat ,, but iam worry that the performance will change ,, and i need to re program again

Get a high flow cat. Done.

My headers are long .. I should search for direct fit ?

What about the o2 sensor ?

I just make it tune for check engine light after remove the cat

No, direct fit may not work in your case. Take it to a shop that can weld one in directly.

You will need the upper O2 sensors, do not remove them, do not tune them out.