Car won't start

[90 GSX]

I got a 90 GSX. It's had a vacuum leak at the intake manifold for a while and I decided to fix it. First I put a new throttle body on with new shaft seals on it because they were leaking too. In the process one of my EGR bolt snapped, so I put one bolt in it with a blockoff plate. When I started the car with the new throttle body and EGR it ran shitty, idled at 600 and felt like it wanted to die. It also made sort of a whistle noise so I decided to take my other car to school. I went to start it after four or five days it would not start after it was running the last time I turned the key. So now I rethreaded the EGR hole, put a new mitsu intake manifold gasket, and another throttle body and after having the car sit for about a week, same problem.

What could it be?

 

[ChicksDigBoost]

Check your normal Fuel, spark and injector pulse.

As far as the low idle.
Check to see if the EGR is Stuck open.
Carbo Deposits can cause this. Pull it off and inspect it.
If it is open @ idle it dilutes the A/F ratio causing low idle and rough running.
You can also apply vaccum to the EGR to see if its opening and closing properly.

I would start there first.