for repo man yes you have to pull them out of the car and yes it has to be a gang car with a gang member driving..
Here is an easy tip though: keep the gang awareness at 0
basically if the little gang meter at the top right of the screen isn't being displayed their awareness of your presence is 0.
when this is the case they'll drive right by you... so you can pull them out of the car. Once you do that those particular gang member will start shooting at you (as will any others in the immediate area) but the gang awareness will still be 0.
Get back out of the car and run/jump to a different area. with a new car... as long as you didn't kill or attack any of them and the meter is still at zero they wont follow you.... repeat the process.
Basically find an area with two major roads separated by a good distance hijack a car on one... run to the other and hijack a car... run back to the first area... etc. etc. etc.
As long as the meter isn't being displayed gang members in a new area will never get out of their car.
As for the orbs, it's MUCH MUCH easier to use a guide if you still have most of them to collect... because if you go to an orb location and there is no orb there you really don't know if you're in the wrong spot and missed it again or if you've already got that one. If the orb is still there, well, then you know you definitely got it.
I used this map: http://www.msxbox-world.com/forums/index.p...c=6765&st=0
and these pics: http://picasaweb.google.com/frodekn/HiddenOrbs/
^ I can guarantee that those are 100% accurate the IGN guide and the orb map in the official strategy guide are both grossly inaccurate.
This site has a ton of good info too: http://www.candiedskull.com/crackdown/
I used it for the stunt ring map and a map of the rooftop/street races). A lot of their stunt ring video strategies I didn't agree with at all... and a good number of them were just "have a co-op partner throw you through" which is BS IMO... I did all the stunt rings myself
let me know if you need help with anything else... I can give you lots of good tips for any of the achievements.