2004 Chevrolet Express 2500 Questions

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Van has been over heating on an irregular basis with pools of coolant sporadically being left under van. Pretty sure it's a bad thermostat but fearful it's also the water pump.
Changed tank and sender as well as the crank shaft sensor still crank with no start. Not sure where o look next
2004 Express van 4.8l with 140k miles.

Past couple years:
Hard to start after fuel fill up.
Random miss and hesitation when accelerating. Pumping throttle would cure. Then randomly again from 30 min to 7 days between.

Missing most of the time, especially when hot. Rough idle and evident miss, no power.

Diagnosis so far:

Throwing P0300 (random misfire) and p0455 (large EVAP leak)

Started with EVAP solenoid at fule tank. Nope.

Purge valve solenoid at throttle body. On first start nope. Let cool and ran excellent. Smooth idle, rev fast, plenty of power. Lasted about 20-30 miles. Bad again.

Codes Reset.

Next plugs and wires. Nope.

Removed catalytic converters. Nope

Took to shop for scan tool. Shows p0300 (random misfire) and p0175 (bank 2 rich). Also shows misfire history. Cyl 2 and 8 around 3000. Cyl 6 33000! The rest are small numbers.

Tested spark at all cyl. Good.

Tested cyl 6 without plug wire feels the same. All other make it run worse. Seems like it is #6.

Tested #6 compression. 150psi.

Back to shop for fuel injector testing (not sure of actual procedure used there to test). They tried MAF and MAP sensors. Nope. They think ECM.

To Local Chevy dealer for ECM check. Say its good. Want $200 to diagnose. Their verdict is cam and lifters...

I have a hard time with cam and lifters. It will run great at times. Used to be run great all the time and random rare miss. Now the opposite. Miss mostly and run great rarely. Does seem to be best when cold.

I am thinking about swaping the 4 and 6 injectors to verify those. Trying to round up a node to test with.

Any suggestions before a motor rebuild?
I just recently changed the oil pump and sensor in my 2004 chevy express however while driving the pressure says 20 then drops to almost 0 what could be the cause?
No DTC's on the scanner but the shop tells me i have a pending coed. I failed the emissions test for PO300 random misfire. That code has cleared. ive drove the truck for about 500 miles but it won't show ready for the EVAP & CAV. A Readiness Result:Fail- Count Of Noy Ready Monitors:2-
EGR System:Unsupported- EVAP. System: NotCompleteed-
Catalytic Converter: NotCompleted- Secondary Air: Unsupported
Sometimes it sounds like it is the battery is dead, sometimes it sounds like the starter not enough power to turn the engine and sometimes it acts like nothing is wrong with it, please help if you may have an idea of what's going on. Thank you.
Brakes with no luck. I turned the cruise off still no luck. I had to turn the engine off. Now when I start it up again it revs real high. HELP PLEASE. I'm sitting on the side the interstate
Where is the thermostat located
to normal. The van never does run hot. What would cause this? Thanks
The panel doors worked off the remote buttons till now.All that happens is the running/parking lights flash when hitting the buttons.It may be that the programming has been lost,but I cant find a fuse/relay to eliminate 'no power' as the problem.I have continuity checked all the fuses in the(pain in the a%$) fuse box.I have 2 questions.1)Is there a troubleshoot chart someone has to trace the problem?2)Is there a re-program procedure for the remote?
At 40-50 MPH the steering wheel shakes bad and all steer linkage is tight
I have changed the bulbs in the rear driver side and also the top stop light above the cargo doors. when the car is in drive the driver side rear and front blinker flASH rapidly all appear to be working but the outside driverside brake light is dimmer on the driver side. when the van is in drive and the headlights are turned on the blinkers are not blinking as fast but the interior front cargo light still comes on dimmly when i apply the brakes and when the turn signal is on.
replaced ignition switch,electrical part
also does the same thing when backing in a steep drive way it happens intermittentley i can clear it out by revving the engine
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