XR4Tim

My vote goes to air leaks. If the MAF isn't getting airflow from the engine sucking air through it, it won't provide the necessary fuel to keep the car running after initial startup.

targa996

I had similar issue with a C280 mercedes - shop had done some work on the car, but then it would not run after start. He asked me to bring over spare key. Same problem. WHen I opened the hood, I noticed the rubber boot for air intake was not seated properly on the intake - I re-seated it - and then the car ran with no problems. The mechanic was highly embaressed. So if by putting the old starter back you re-attached some of the air intake hoses - that could have been your problem ...

logray

If you had a huge air leak the car would probably run and it would sound like absolute crap. If you want to see what that sounds like you can pull back one of the boots and create a big air leak. It runs, but just horribly so.

I would take your new starter to an auto parts store and have it bench tested for free. If it checks out OK, I would reinstall it, being extremely careful to get all of the wiring back together correctly.