That was one of the thing I suspected last summer, so I getted rid of the precat and cat, I dont think the exhaust is my problem... I agree that it could had been it!
I hope you are right, for the water at the exhaust...

The problem is not easy to resolve like I said, its uncommon...

You guys have to check my ignition tension wave, I'm sure the problem can be saw by looking at it!

There is REALLY a Demon in my engine, even after like 100 post and reply alot of diagnos, but the solution is still not there.... If it wasnt the 13mpg, and the lamda value at higher rpm, I would thought that its only my imagination...

The engine was rebuild last year, by the last owner of the car, I suspect it was principly 'cause he tought it was the cause of the lost of power, but it didnt helped alot so he deceided to sell the car... to me...