[goodhart]

I'm guessing by coilovers, you mean coil springs? If the previous owner heated the springs to lower the car, you would probably be better off with getting a set of used springs to throw in there.

For the other issues, bring your car to one of the shops mentioned before for a quick diagnosis. Also it wouldn't be a bad idea to make sure it is tuned right. With many of these hacked together cars like this, it isn't uncommon for them to not be tuned right and just be a ticking time bomb. get a boost gauge and drive it VERY nice until you get the car looked at.