idles rough and erratic

You're running rich, you have unspent fuel burning in the exhaust - the reason it's cherry red and you smell gas. Can be from a number of causes, if it was only the front side exhaust it was affecting one bank and not the other. Get it diagnosed, you may also be setting trouble codes so have those read, that will give you a good clue what's going on.

What r the cause for that? it doesn't give me any codes

That will require someone to inspect and diagnose. You have a throttle body and fuel distributor rail, the rail may be leaking. You may also not be firing correctly, leaving unburnt fuel to get dumped into the exhaust manifold. Excessive carbon buildup on plugs and repeated stalling can cause the computer to get wonky and run the air-fuel mix to rich. The fix may be fairly cheap and easy to do, but you need a proper diagnosis to know what to do, so take it to a mechanic.