MAFs are one of first things to try according to P030X diag flowchart.

 

I could see that just didn't imagine it for very specific cylinders. I'll def. Try it.

 

What do you have to lose at this point? That estimate is astronomic and even if you source used exhaust parts and cat - absolutely no guarantee that it's going to solve it.

 

How many miles?

 

155,000 miles

 

From my research, cats are more likely to clog/fail from short city driving as they require highway induced heat to self clean. Your mileage is low for a 15 year old car. Hard to say if this is because of city use or just low usage.

 

It was badly misfiring when i bought it. I fixed all of that. I'm curious if this is a result of them driving the car with it misfiring. I have the carfax, well maintained and local. Could be short trips

 

I'm following/questioning the cat diagnosis. Were there any error codes that point to this being an issue. Based on threads here, dealers sometimes play loose and wild with suggested repairs. You didn't say if the dealer concluded that the cat/exhaust is the entire issue. Have you considered taking the car to an indy shop that advertises, Japanese/Lexus specialty? Might be $200 well spent for another diagnostic opinion from someone with hands on your car.

 

Just drop the front flanges of the y pipe and you can inspect the back of the primary cats yourself, you seem like you know your way around your car.
You won't be able to see through them with a flashlight because of no light on the upstream side but you will see if the interior is damaged.

 

MarPov95 I'm curious did you get your 5 / 7 misfire resolved?

 

unfortunately not yet. Mostly for lack of time.

 

On you spark plugs, exactly which ones did you use? The 2 post ones are known to cause issues.

 

I'd have to look now. I'll look tonight and let you know.