Dieseling and Slight Backfire - 250I6

[Mike-P]

Hi Everyone,

Ever since I picked up my truck, I've noticed that it has been dieseling slightly (Idling a bit after ignition is turned off, 2-3 seconds). Additionally, when I am gearing down, I thought I was hearing a slight backfire in the engine compartment. So, after running some sea foam through the oil/fuel and changing the oil and filter, the problem still persists.

Today, I thought I would check the vacuum on the carburetor as perhaps the air/fuel mixture was slightly off and perhaps the truck was running lean. After getting under the hood, I noticed some black exhaust on my block. I'll attach a picture, it appears as though my exhaust manifold is either cracked or not sealed properly. Anyhow, going to look at replacing the manifold.

Would it be fare to assume the dieseling/backfire is coming from this?

Thanks for your input,

Mike