Saturn car unusual problem

I appreciate the help. I have done much research since the time I posted the original problem. Here is what I found. They replaced the 94 motor with a 96. The 94 saturn is a tbi. The 96 is a mfi. It appears they changed everything required on the motor.(Except for maybe an incorrect installation of the spedometer cable and maybe an inoperational temp switch). I havnt touched it in a while it isnt my primary vehicle. As for the tach stopping at 4 instead of 6 or seven, I am not sure, but I believe it may be a problem with the computer. (Like someone maybe installing the computer from the 96 or not connecting it correctly. I will give the codes as soon as I can get them again. I got the codes with a paperclip from the receptical for the code catching equiptment that the professionals use. My check engine light flashed the codes. Anyway even after looking up the codes in the autostore the man who worked there who has been very useful in the past was confused and said I may need to trace wires and he believed that it would lead to my computer. On one of the codes he was able to locate an electrical component for my carburator that needed to be replaced but the component didnt match the one in the car. I believe their may be multiple problems but I want to know for sure before I spend 200 bucks on a computer and 200 bucks on a egr valve and so on. I bought the car for 200 bucks and I have definately got my moneys worth but my mother loves the car and would like to see it work correctly. I think it would be the computer that would make the governer kick in at 4grand instead of 6grand but I am not sure. Someone recomended egr valve replacement but it appears to be doing its job to me. I wont know about the speedometer until I tear into it and I wont know about the temp switch until I replace it and/or splice the wires that are next to it to see if it may be the wrong wires. If you have any advice I would really appreciate it

I almost forgot. The differences I have discovered between the 94 and 96 motor are as follows. The 96 has fuel injection and the 94 has a carburator. The intake is different. The egr valve and the engine computer are different and the wireharness. I believe that is it but I am not 100 percent positive. It feels like the car is missing when I am driving and it is annoying accidentally hitting the governer all the time. Thanks for the help.