I've put in a new TBI engine in my 89 burb. of course the CEL is now on. I'd like to check the codes. I can find a number of OBD1 scanners on line for sale from $40 to $200. Which are best? also, how do they work, the cheaper ones don't seem to have a display??? should they all have a display? Or do some need to be plugged into a computer?