OK so after several weeks of having loping idle and multiple codes for MAF MAP IAT and diagnosing troubles as wire connections and bad sensors finally got my 98 running, somewhat. Now I'm getting consistent P0304 code and poor mileage, fuel pressure test runs consistently at 62PSI even after 15 minutes after shut down. Replaced a couple sensors which helped with idle and running but still erratic then smooths out, then erratic RPM again with stumbling almost to point of stall. On a side note I also notice my auto door locks engaging randomly, is it possible to be BCM or ECM related from bad ground? Any help appreciated

 

Well that is a cylinder 4 misfire code, should be pretty straight forward to figure out. Cap, sparkplug wire, plug, loose plug, bad injector or leaking valve, in good to bad order. I had the same issues one time and hunted for a week, it was a loose plug LOL. This is all to do with cylinder 4

 

I'd check the compression on cylinder 4..If low, it aint going to be an easy fix.

 

Did the plugs, wires, cap, and rotor all 6, #3 wasn't an easy one! Driving to day had a consistent STFT on B2 -30. Thinking must be the 2, 4, 6 side? Does that support the bad injector for #4 cylinder

 

https://www.obd-codes.com/faq/fuel-trims.php

 

Thanks newguy, confirms my suspicions on the misfire. Happily it's narrowed the search to specific cylinder, I can compare visually between the injectors to determine if it's the spider or injector

 

When you take off the plenum if the intake is shiny/clean in areas you have a leak there. Its supposed to be carbon black