Need Info. Weird Sound at cold start up

[lasgambler]

Hello. I have a 2000 PSD, auto. I recently installed a TS Performance chip and have been running the truck on the 75 setting. 2 days ago at cold start up in the A.M. It would start, but lope severly RUMP----RUMP----RUMP. several times and then idle out smooth. It did this 2 days straight, Then today before starting I set chip at the stock setting. Well it did the same thing. Does anyone know what the problem might be, or have you heard this before? Thanks Terry