[Reiver]

I have an '83 Euro SC with the later airbox/diffuser and pop off. I did have a backfire last year and the pop off saved the box from any harm...the pop off lid put a dent in the air filter.
Glad I have it.
Somehow the AFR had leaned itself out over time.
I've since installed an onboard AFR system/gauge and monitor it all of the time.
It is great for tuning the car for winter/summer variances.

The AFR can change for no apparent reason and the car run very well.
On the Euro the wur is critical too as it controls mixture as opposed to the lambda on US models.