I have an 98 a4 and it's having a lot of problems starting. I've changed spark plugs, checked compression, checked sensors, checked air filter, changed fuel filter, and replaced the valve cover seal. Now the problem is worse than ever before. The only thing I can think of is maybe it is a fuel pump problem. Anyone else ever have this problem?? The problem occurs when the car is cold started.

 

I have had this issue on my 98 a6. It won't start, I have to crank on the engine for 5 or 10 min, if no good I have to wait an hour or so to get it to start. I had a bad camshaft position sensor, replaced it but still had the issue sometimes. I think I finally nailed it down to a vacuum leak on the hose that ran between the valve covers. Once there was no leak on the hose the car seemed to start much better. Not sure if it will be the same issue for you or not?