99 Jeep Wrangler Sahara Sputtering Problem

[ValuPaq]

I own a 99 jeep wrangler sahara 4.0 6cyl with 3 speed auto. I am looking to sell this vehicle, so I dont want to drop a lot of cash into it. My problem is that randomly the engine sputters like i am losing a cylinder. Two weeks ago I changed oil, plugs and wires with bosch platinum 2’s, (unknown at the time that I had bosch platinum 4’s in the vehicle already). I degreased the engine compartment being careful not to spray full into any electrical devices, or the air box. I also changed the exhaust to a cat-back 2.5" system, which was a bolt on application, and might have a slight leak. Would any of this have an effect on my sputtering issue. I have already check all my plug wires for bad connections, or wires touching hot areas in the engine compartment. Any ideas you have would greatly help. thank you