I searched and found a few Posts on the subject, my post is to tell you, it is true...

I've owned my 997.1 TT since 2015. Bought it w 82k miles and now have 109k miles. I bought an exhaust system within the first 6 months.

CA. smog check is every 2 years, you can not have a modified exhaust w high flow cats of any type. So, every two years I have to pull the aftermarket exhaust, put on the stock system, go get it smogged, pull the stock exhaust, put the aftermarket system back on and have fun for two years.

During the last couple of years I have been wrestling with some medical stuff so I haven't put many miles on her. I've been chasing the P0134 Bank 1 sensor 1, I believe. I would clear it, disconnect battery etc. and the code would come back in under a hundred miles. May 2021 I decided to pay a local Indy shop to tackle the exhaust and take it to get smogged at his local buddies smog shop.

After 50 miles or so, up pops the P0134 code, again. I was done dealing with the Indy shop, long story. So I figured the O2 sensors have 109k miles on them and have been taken on and off several times during exhaust swaps. I replaced all 4 sensors w Bosch from my favorite parts house.

Drove for about 30 miles and P0134 again.
​​​​​I decide to do a lot more searching on forums for other possibly causes. I found a few posts that said they heard that sometimes a dirty throttle body could throw a P0134, I kind of had a tough time with it but decided what the heck. I pulled the TB off and much to my surprise the back side of the blade and bore was pretty gooey. I cleaned it up w good guy MAF cleaner, put it back on and have 250 miles on it with a much smoother running engine and NO CEL!

Crazy but true...
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Thanks for sharing!

 

Great news! Thanks for sharing this tip.