Gigablast. I'm getting consistently occurring latency spikes of 250ms on upload (only while under load)

Its been this way since I moved to my new address(5 months). I've been through 2 top of the line modems. Used 3 seperate PCs to run tests. I went as far as to run a coaxial cable from the ground at the house, to the modem, bypassing all house cables and my xr500 router. 3rd tech came out today. He fixed a bad spot on the downstream side at the pole. No luck on upstream. Problem is still there. My household is streaming only, which this causes a problem for. It also makes online gaming just inaccurate enough to not play anything with confidence. I'm frustrated beyond belief. Any ideas?