904 / New Converter, abnormal noise

Hi Guys, got some Trouble with my new installed 8" custom made converter. I proudly put it in few days ago, made a test drive today (around 15 miles). When i was back home i noticed a strange noise in P and N, in D it was much less noticable.

Put the car on the hoist, clearly coming from converter area. When i rev it, the frequency of the noise is going up also, but with little delay. I noticed when i shut the engine down then there´s still some of this noise for a second. I think sth. went wrong with the converter, sth. damaged inside. What do you think? Any way to check this out better?

Dont want to kill it and my trans, too…..



Michael