Engine Performance problem
2000 Other Opel Models 4 cyl Two Wheel Drive Manual 110000 miles
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I have to replace my Catalytic converter and the pipe that connects to the bottom of the manifold. I ordered one from a shop a few days ago and although the guy input all of the car information correctly (i was sitting next to him facing the computer screen), the one that was sent was not even close to the right thing. Oxygen sensor hole in the wrong place, brackets wrong, etc. although these were the parts listed as being for my type of car.

I went to another shop and tried again. After comparing the old and new side by side, they appear to be the same other than the Cat being a bit smaller in diameter.
The problem is, the label on the Cat/pipe (it came as one already welded piece) states that it is for a Vectra with a 1.6L engine. I have looked at the part online (Walker part # 20238) and it is not listed as being compatible with the Vectra with a 1.8L engine.

Is this going to cause a problem?