Code 19 is an adaptation limit excess code..it is also common on that chassis b/c the ECU had a small percentage +/- lee-way for limits before popping the code. That can be expanded to a larger % by changing the chip in the ECU [ do a search on code 19/JimF here]...

..but , before going that route, you want to check for BOTH vac leaks AND fuel pressure. A vac leak will cause ECU adaptation beyond limits to correct for the lean condition caused by the leak, and a bad FP regulator will cause a rich condition by leaking gas into the vac port of the reg or allowing too high of a FP. That rich condition will also try to correct , but if the system has to correct too much , same deal...pops the limit reached/exceded code.
So, I would check for both vac leaks everywhere and then I would check the FP regulator and pressure.
If the engine has many miles , then it is just in need of a higher adaptatation value than the ECU is capable of and the chip w/higher % limit can be done..but don't do that until you have checked the above first, as you may not even need higher adapations % limits.


EDIT *

Jim F and I were typing in the same time frame, so his Posting is the search notation I was referring to............he has those chips, if neeed.

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A Dalton