I have a 99i30t and for the past 6mo or so have had a slight gas smell at the exhaust -worse when engine is cold. a few weeks back, it finally turned on the CEL and I had the KS and front cat replaced. From then up till now, the smell has changed to something very similar to burning charcoal (BBQ charcoal). The exhaust also seems like it's spitting more meaning it's not steady stream when you put your hand there.