Clean Cats
 

I have read a couple of threads about removing the Y pipe and washing the CATs, is that a good practice? Does it make sense?
Also does someone know the real difference, if any, between the Oxygen sensors on the Standard Evap system and the Advance Evap System other than the connectors? I know they change in 1997 from one to another, but I believe the only difference is the connector and a bunch of money.

Buy the O2's on Amazon, they have the best prices.
I do not know if there is a difference in the O2's other than the connectors.
As for washing the cats? Cats hate water, they will cry and scratch and do whatever they can to get away, dont do it.

A man that can wash his weight in house cats is truly a man...oops - wong cats..

Heres a video on two shade tree ways to do it, one with a plain solvent, no removal required. Fixing Bad Catalytic Converters With Inefficiency Code P0420 - YouTube

I dare someone to dump a gallon of lacquer thinner into their gas tank.

Well, how about some CRC? CRC Industries | Automotive, Heavy Duty, Marine & Hardware They make a good MAF cleaner... but people will put anything in their tank it seems. Acetone, laquer thinner, sheep oil, etc. Won't make up for 50,000 miles of slow driving on regular gas...

I talked to a industrial chemist a few years ago when the whole acetone in the gas tank kick was going big.
He said it does nothing to increase MPG like people claimed, he said that you cannot change the molecular make up of gasoline without actually changing the production process.
And all that those people were doing was ruining their injectors because that much harsh cleaner was not good for them.

Since I just posted on another thread about this...
BG Findashop - Search for an authorized BG service center near you!
The shop I used to work at was a BG shop. When a vehicle came in with a P0420 catalyst efficiency below threshold code, the BG induction service was the first thing recommended. A few vehicles needed the service twice before the code was not gone. These were vehicles that other shops would have replaced the converter. After the proper cleaning(s), we NEVER had a comeback.

These were all vehicles with a "failed" converter. Granted, we did replace a few converters, but the majority were cleaned with the induction service.