Just applied some UEC to one of our WRXs and I noticed the vacuum line had split when I reconnected it to the manifold.

I've done a quick search and found a discussion where people were arguing whether the inner diameter should be 3.5mm or 4mm. Then the thread ended with no resolution...

Can anyone tell me for sure which ID I should be looking for? Initially I just want to pick up a short piece to fix this split pipe, but eventually I'll be replacing them all. I don't want to screw things up by using the wrong size, or alternatively I don't want to go chasing some hard-to-find size if near enough is good enough.

Thanks for any replies.

I just changed all of mine on the gc8 with 3mm silicone hoses.
3m length from auto one for $25 or so.

__________________
Straya

Thanks for that. The one on the other car just split as well, and all the originals are as hard as copper pipes. Will get some 3mm tube and replace as many of them as I can.

just be aware that some have the restrictors in them in the wastgate line

Yep, thanks - I've been reading about brass pills, brass olives and bronze nipples and ... oh wait, maybe that last one wasn't on PWRX.

mmmm nipples nom nom nom