i'm not sure why i'm getting a lean error code.

When i start the car my gauge says its rich then as i drive for the 1st minute it slowly makes its way down to lean and the off the gauge. Before i gutted the cat it would bounce back and forth at idol like it should now it doesn't

I did gut my cat so i think that the o2 is giving the ECU rich readings so the engine is ECU it lean.

What should i do get a new cat, o2 simulator

HELP

 

REVISED the end of the 1st is confusing

i'm not sure why i'm getting a lean error code.
When i start the car my gauge says its rich then as i drive for the 1st minute it slowly makes its way down to lean and the off the gauge. Before i gutted the cat it would bounce back and forth at idol like it should now it doesn't

I did gut my cat so i think that the o2 is giving the ECU rich readings so the ECU is making the engine lean

What should i do get a new cat, o2 simulator

HELP

 

I'm sorry I dont really have an answer but what happens when you wanna get a dyno done and your going to use a test pipe instead of the cat. I havent done it yet but I was going to in a month or so. Im sure someone who has done this would have some info.