Cannot get past 5000RPM with 5.7L TBI

[MuddiGGEr25]

The engine is a 1987 5.7L TBI in a 1988 V10 suburban with springs axles, and shocks from 1984 K20 with C6P HD package

https://www.youtube.com/watch?v=ls2reqsONyc

https://www.youtube.com/watch?v=sNKU5L9gbzY


as the video descriptions say one is at idle, and one is in D and R all within 90 seconds of starting at 34F this morning, and it sounds like a random miss when cold but once warmed up it is very consistent, and I know it is on the drivers side for sure.  I cleaned all plugs with carb cleaner and all 8 were replaced with Bosch+4 platinums about 2 months ago i think. and  i usually have good luck with the +4's, the wires were replaced with the plugs but one had melted and i replaced that one too.   one of the +4's broke off by accident and I replaced it with a fair condition copper but did not seem to affect it at all

I have a replacement +4 arriving tomorrow, and I intend to also swap out the other 3 wires on that side with known good ones tomorrow as well just to be on the safe side.

Replaced the dizzy, cap, rotor and put in a known working 369 module and the dizzy was fully functional when pulled.
Ignition coil tested within specs last time i checked it and a new coil made no difference


It sounds like a standard exhaust leak except the exhaust on the drivers side can sometimes suck in a dollar or paper if i hold it in front of it. the condition got better after i checked the rocker arms and they seemed more loose than they should be so i tightened them.

And the noise goes away when in gear and no miss while under load uphill or while drag racing.

However I cannot pass 5000RPM at part throttle or WOT anymore, when I am racing i hit about 4800 and it starts sounding absolutely horrid then not matter the throttle position I cannot get past 5K, however just before I had the dizzy issue I was able to very easily reach 6000RPM all day everyday, and there are videos on that youtube channel showing the scanner even registering 5950RPM before i let off the throttle.

Trying to figure out if this is mechanical or electrical, The timing is at 3 BTDC and has excellent response from idle until it peaks right around 4000 then i shift.

o2 is disconnected because when cruising along at any speed over 15MPH it starts to either cut fuel or timing to the point of almost stalling then catches itself and repeats this indefinitely. the speedo is wrong and I will be ordering the proper gear for the TC to correct that in case the ECM is using incorrect speed values to set the fuel trims.

It was still running very well after hauling 11,000+lbs up from SD (270ish miles)

It started acting up after going through a really bigass puddle and water got in the dizzy cap because it wasnt tightened all the way.

[MuddiGGEr25]

If i downshift while intown say at 45mph or under to use the engine to get me to slow down or if i want to stay in a particular gear while racing then i do have alot of noticable popping ask the RPM's decrease

[MuddiGGEr25]

I swapped with all known good wires, i had high tension on there but replaced them with delco's and replaced the odd plug with a brand new matching one, still does the same sound, im beginning to think i might have to pull the heads after we get back in june, if they even make it that long. i did an oil change today also didnt make a bit of difference. the exhaust is leaking just a tad but i will tighten it up in a week or so and see if it makes anything better

[Irish_Alley]

hows the valves? fuel psi? im shooting in the dark here, it seams as if youre knowledgeable in the engine part.

[MuddiGGEr25]

Valves are unknown but was fine until idrove thorough a puddle about 2ft deep and splashed water and ended up needing a dist. Im afraid it might be a valve problem but they. Were fine before, fuel psi is. Fine runs fine up tl 3800 rpm towing 1-3K