Recently my I heard this pulsating sort of harmonic noise while driving my 81 245 and realized that it corresponded with the an almost chattering sound coming from my 6 month old main fuel pump. So, I replaced the main and the in-tank pump, and my car was quiet until I had driven it for about 45 minutes, and then the noise was back, big as life. New pumps, new filter, new strainer and this obnoxious and unhealthy noise. What is going on? I have also recently had a condition where my car stumbles and hesitates for a few seconds when I first start it, and then it clears out. Could the two be related. It is the old k jet style injection. Any advice and insights would be appreciated.

Pete