Congrats on the relay, with a Google search,ipc/dic fuse on 04 Tahoe, radio comes up most,then, headlight switch,then, just about anything the cluster displays,yikes, process of elimination
Some of the h.d.s',have the driveshaft yoke clunk like the 1/2ers,g.m. sells a synthetic lube #19257121 that's compatible with tranny fluid to lube the splines on output shaft of t.case?
?,time to eliminate any non-essential fuse and relay,or modules,one by one,great good man,a wiper motor assembly can take it down,it all depends on how a module failed
I wouldn't clean under egr with manifold on, maybe cause a issue,you can't correct without disassemble,so new pcv,can't hurt, possible vacuum leak,spray test on vacuum lines,and with a flashlight,watch injectors for a nice cone spray pattern
You could spray some carb cleaner on all vacuum connections all the way to the booster,listen for idle change,and what about p.c.v?stuck open?as far as the cleaner?how dirty was it under the egr? thinking, carbon on backside of intake valves,think another round of cleaner?
#4,dirty, obstructed wheel sensor, whichever side it pulls to,clean opposite side,#3,you mentioned high voltage,but not low,could be too low,change the alternator,#2,could be solved by same change,#1,scroll down to ask the technician, possible cluster fix