Have you put your original stuff back on and reset the code? I would try that for a few weeks and see if the code comes back. 
P0430 after SLP lid and MAF?
P0430 after SLP lid and MAF? I just put a used SLP lid on my 02 ws6 I bought off a member here. He sent along the lid and also the MAF and IAT sensor since he had trouble getting the MAF out. The car has been running great. Power is up, idle is better and it's got better throttle response.
However a couple days ago it threw a P0430 code for the passenger side rear o2 sensor. I switched the rear sensors side to side, cleared the code, and it came back again for the same side. So now I know the sensor isn't the problem. Looks like my CAT is shot on that side.
Before I go spending money on new cat's, is it in anyway possible that the things I just put on could cause this? Lid not sealing? IAT not reading and pushing too much/not enough fuel? MAF sending bad readings?
However a couple days ago it threw a P0430 code for the passenger side rear o2 sensor. I switched the rear sensors side to side, cleared the code, and it came back again for the same side. So now I know the sensor isn't the problem. Looks like my CAT is shot on that side.
Before I go spending money on new cat's, is it in anyway possible that the things I just put on could cause this? Lid not sealing? IAT not reading and pushing too much/not enough fuel? MAF sending bad readings?
Oh well, I'm out of suggestions then. I thought you might have gotten a bum MAF. The IAT sensor is just a thermistor that measures the temperature of the incomming air. Its either going to work, or not. Nothing to 'wear out' in that sensor. 
Maybe someone else will come along and have an idea? It's out of the warranty for the cats. Too many miles.
MAF is a stock one that still has the screen. I did a little research and found that sometimes the SLP lids don't seal right. You have to kind of force them under the front "lip" of the bottom box. So I did that and the clamps are definetly tighter now. Will clear the code and see what happens. Doesn't take more than 15 mins of run time for it to pop back up once I've cleared it.
I've also checked the voltage of the sensors with my scan tool while the car is running. From o2 voltage varies like it's supposed to, rear stays pretty much the same.
MAF is a stock one that still has the screen. I did a little research and found that sometimes the SLP lids don't seal right. You have to kind of force them under the front "lip" of the bottom box. So I did that and the clamps are definetly tighter now. Will clear the code and see what happens. Doesn't take more than 15 mins of run time for it to pop back up once I've cleared it.
I've also checked the voltage of the sensors with my scan tool while the car is running. From o2 voltage varies like it's supposed to, rear stays pretty much the same.
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Mini... The air lid sealing or not would not cause that code. The MAF is downstream from that seal and the only thing that would be affected would be unfiltered air might have contaminated the MAF sensor. If you do not run through sandstorms, fields of freshly mown growing things, swarms of bugs, or anything else that might slip past that seam, I would not focus on that fixing your problem. Its good you fixed the seal (you did check if any debris was on/in the MAF before resetting the lid right?), but I think you have another issue with this code popping up. LS1 Tech Stories
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