I'm just curious if the test listed in the TSB is definitive for plenum leaks (it makes it sound like it is...). I checked for vacuum in the crankcase using the test in there and there was none-- after 30 seconds it goes up to 1.5-2PSI of pressure. I'm getting a catalyst below efficiency light periodically. I replaced the upstream sensor first because the exhaust was stinky, and it now smells normal, but I'm still getting this code and have a sporadic rough idle. I'm going to replace the downstream one (it's all nasty and rusty, looks far worse than the upstream did, at least on the outside).

I'm not using in inordinate amount of oil at this point, and the plugs look fine.

So my questions:

Is that test a flat "yes there is a leak if you have vacuum, no there is not a leak if you have pressure" so my gasket is likely good?

Also, does the downstream sensor affect mixture at all? In previous vehicles I've had it doesn't but just want to make sure.

If it is the catalytic convertor, what couuld have made a 7 month old cat already go bad?

Thanks!

Not sure on the plenum. However, i can help on the others.

No, the post-cat O2 does not control the mmixture.

Was the smell you had similar to rotton eggs? I know that is off the wall but the cat can make that smell if its going bad.

It smelled more rich than anything... sort of a dirty old car smell. After I replaced the upstream sensor that went away. I've heard that a bad cat can smell like rotten eggs or fireworks... I've smelled neither. Hopefully it's just the rear O2 sensor...

Anyone have any idea about the plenum/crankcase pressure question?

yes that test is accurate for a blown plenum gasket.

Shoot. I have new o2's and my new high flow and I get that firework smell if I get on it like WOT. Nothing at idle, dont smell a difference, but if I run her hard for a while I get that smell like someone just set of fireworks. Am I the only one or is that standard for highflow's?