With no codes, it is either a mechanical issue, or the failing electronic component has failed enough to trigger a code.

Might start with the fuel system, replace the filter and possibly the pump.

May want to pull and test/clean the injectors, check youtube for a DIY video.

From there start testing ignition components and the air flow sensor, in my experience if/when the components are near their extreme ends of their operating ranges, they are usually the issue.

Other areas to inspect.
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More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed