I do believe I found the problem on my 98 Ranger. Pulled head and took it to machine shop that is highly reguarded for their work. Guy showed me the problem. all exhaust valves burnt and seats bad.. Said most likely cause from past experience was fuel. Now I need to clean throttle body and Plenum parts as they have lots of carbon build up in them. What do I use for this? Is the 2.5 not used much. Do not read much online about it from other Ranger owners.