battery swap issues

Hi Im a new VW owner I have a 99 passat gl and its been running fine for a few months and recently Ive been having to throw my charger on it in the mornings to get it started. So the other day I got a new battery for her and hooked it up when I started it for the first time with the new battery it cranked over a couple times then fired but died. When I tried to restart it sounded like the engine was spinning with little resistance. I was instantly angry and held the pedal to the floor and in a couple seconds of cranking it started to stumble then started it ran like crap for a few seconds then did fine the rest of the day. This morning it did the exact same thing so I repeated the process of pedal to the floor and it started again. I took it out for a drive and it started fine everytime I shut it down. I left it outside in the weather for the night to try it again tomarrow. Any ideas? 99 Passat with 110k mi. 2.8 v6

Did you ever get any responses to this. I just changed a starter on our 1999 Passat. Had the battery un hooked while changing it. Now my car does exatly what you said yours is doing. Starts and dies. If I rev it up after starting I can keep it running for a short time. As soon as I let off on the gas it dies.

No I never did get any input but...... mine did not die when I let off the throttle I would hold the throttle down to keep it running untill it smoothed out. However it is running fine now that problem only lasted a half a dozen times then oddly just "fixed itself" Hope its gone for good but I doubt it. maybe someone who knows will come across this post.