im thinking about picking up a diagnostic machine after the last couple of weeks. but i dont know whats a good brand. does anyone here have one for there own personal use??

If your referring to a diagnostic for your Jeep I went with http://www.digimoto.com/ for my Jeep with a Vortec V6 and have been very happy with it.

If you are referring to a basic OBDII, I bought one off ebay for $40 I think. It gives me codes specific to the Jeep (don't know about the engine replacement)and the other cars in my growing fleet.

I have an obd2 reader that is part of my laptop. got it on the net for less than $100. It has paid for itself many times over.