Starting problems and sputtering

I have a 94 jetta GLIII(the first car I bought).
It currently has 154k miles and I have been having problems with it starting. For the past year I have been experiencing starting problems. When I park with the front of the car faceing down hill or if I leave the car parked for a long time I notice a problem starting the car. It will crank over but it will not start. Since I have a manual, I have been in the habit of parking the car up hill with the front of the care facing down hill, and then putting the car into first and turning the car over just long enough to get the car started. Then I quickly shift the car out of gear to let it idle.

Second problem,
When I drive after first starting the car I get a problem with acceleration. Sometimes it is jerky, I mean I will be in low gear and low rpms and the car will learch like I am pressing the gas letting off pressing the gas letting off (The learching stops after I have been driving for awhile). Or it sputers and I lose acceleration and have to compensate with the gas pedal until I get the car to act better.


I have had the car into the vw service and they replace a crank sensor; however, that didn't fix the starting problem.
For the second problem(s), I don't know what is causing the sputtering; however, I know that the exhast manifold sounds like it is rusting out and that the catylitic converter needs replaced. Could this be the reason for the learching on driving the car. Like the back pressure is getting messed up?

The funny thing is that the dealer ships say according to the computer, that it is working fine. Can someone please help me out cause I don't have a lot of money to waste and I would like to make this car last as long as possible.

Thanks

I had luck with this once...Maybe (MAF) Mass Air Flow Sensor = delicate part, gently pull it from air box, clean inside and the filament VERY GENTLY w/ q-tip diluted w/409 or mild cleanser. Replace air filter too if it's dirty or has oil blow back.