Does it even drive? If it just burps and sputter when you give it gas to take off driving but it idles fine makes me think old fuel, maybe there's moisture in your fuel. You said it'd been sitting up for a while, check your fuel pressure too, to make sure you're getting enough when you're attempting to give it gas. Start with fuel delivery then move to ignition.
Could be bad fuel. Gas that will run the engine idling, could not produce enough power to keep engine running under a load.
If you have a obd1 scanner that does real time sensor data, I would take a look at the readings. Idf unsure of what sensor readings mean, pm me with your e-mail address and I'll send you pdf file of "sensor readings and what they mean.
If you don't have a scanner, ebay or amazon usually has the actron CP9145 obd1 & obd2 combo scanner for around $140 Good price.
Or you can turn your laptop into a scanner with the program DataMaster or freescan. I prefer DataMaster because it logs senor readings to a file you can playback in real time. Thus you can share the file with members here to help you interpret the data. If you want Freescan, I can send you a copy.
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