Coolair have an online chat facility which is fantastic as I’ve gotten plenty of advice off of them for parts for my Beetle. I’d use this on Monday for advice and if they can give some information on previous testing.
They're pretty good. I've used a few sets without any problems. I'd say it gives a very small but noticeable increase in "pep". (But so would new rings on old pistons!)
That's a good price at CoolAir.
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The Campershack - (website paused) WBX Rebuilds & Upgrades from the beautiful Isle of Arran
If its within reach its always best to fit new barrels and pistons
The water-cooled doesn't distort under heat like the air-cooled engines do but considering the age/mileage of our engines these days id say they're well worth it
1989 Crewcab 1600TD JX - Gone to Romania
1989 Caravelle 1.9 AutoBox