Well I don't smell anyything like rottewn eggs but my mpg is down to 16 from 23-24 and o2 replacement did absolutely nothing to help and in fact it continues to drop (18-->16 now) even though car runs smoother with new o2. Power does feel a bit laggy so I bought a straight pipe and plan to do a cat elimination after I compression test motor to rule that out. Anyway has anyone seen that big of a MPG loss due to a bad Cat even though the power loss wasn't COMPLETELY obvious? The other thought is maybe a clogged fuel filter and I'm also curious to know if that could cause such a huge MPG drop? This is on my 1g 2.0 N/T A/T, thanks.