No way you live with that. Something's going on. Either look at the motor mounts or the header install. It's so fricking tight down there it ain't gonna take much to touch. Even if you have to clearance the header a tetch with old Mr. Ballpeen that's better than living with what you are describing.
1 7/8 is a big tube and I'm not convinced a tube that size is necessary unless you're doing hardcore racing. Troubleshoot for the cause of contact. If you can't find it then dimple the tube for clearance. No, it will not have any effect on power.