I've done quite a bit of intarsia, but have never had a tension problem. All I can say is that when I switch colors, I just hold the old color over to the left and bring the new color up from under it. When I purl across the back, I think I give it a little pull to snug it up, but that's it.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry