Thanks for the tips. Yeah I think that my wire feed speed was set too high in some cases. I think because it's a 110 v welder I need to bevel the thicker metal, like the roll bar. (I only did this in one area)
One thing I did last night (on the underside of the car) working on the sub frame connectors was to sand blast the area I was going to weld, in case the grinder didn't remove all the paint etc. The other thing I did was move the ground clamp over closer to the area to be welded and make sure that it had good contact.
Thanks for the advice, and tips