I used to make my escapes by stunting when I was chased by the cops in MTA:VC.
And no, it was not the good old rooftop office. I bumped off poles to reach roofs etc. Or perform long distance jumps to get away.
I have done it in SA:MP too against some cops. Stunting my way away from arrest.  :cool:
There's an jump somwhere in Los santos which will enable you to get away cleanly.
Another one is near the stadium at Los santos. There's an tree there that got an / looking roots. You can use it as an ramp to get away, because the cops who are following you might not think about jumping off the roots of the same tree, which in turn will give you an huge getaway because they have to drive like 400 meters around the fence.