So I have done a bunch of testing and still have problems.
Here is a recap…
I replaced the clutch (SB stage 3) and did an upgrade to IMS K26 Billet turbo with associated bits (RS2 EM, "Green Giant" injectors, EFI Express chipset, 3 Bar MAP Sensor)
Everything ran properly for a couple days but I had an overboost condition that was caused by a soldering issue on the MAP sensor (no signal to tell N75 to cut boost). Before we realized the MAP was bad, Marc sent me another boost chip thinking it could help. I did a boneheaded thing and installed the second boost chip backwards which blew the ECU fuse 2x before I realized the issue. I put it in correctly and did a test drive, had overboost again and started experiencing idle issues. The first overboost also blew the crosspipe off the turbo to crosspipe samco hose with a loud bang.
I have a rough idle that acts differently when the engine is cold and when it is hot
When cold, it barely starts and idles very rough. The vacuum rests around 8-10 psi but the car idles at 800 RPM – though rough. When you increase throttle the engine cuts out and dies. If you are able to get it to not cut out, it will eventually rev and pop a little bit.
When warm, the engine will rev and build vacuum to 20 psi or more but still idles at only 10-12 psi rather than the 18psi that was normal. See video…
So I have been trying to narrow down the issues….
Mechanically…
I have verified the timing of the engine – all good:


I have also tested the Compression
1- 168
2- 165
3- 160
4- 155
5- 162
So that should rule out any mechanical failure of physical timing or broken / stuck valves or anything like that.
I will address the work I’ve done in categories...
AIR –
The most popular suggestion was an issue with Air – a boost/Vac leak or a broken check valve or some other part of the intake system/PCV system etc.
I have pressure tested the samcos, intercooler and crossover pipe, tested the vac hose that goes to the ECU, Boost gauge, and through the firewall to the HVAC system. All are good.
I replaced the one way bleeder valve with the 034 Billet version and silicone bits, replaced the pressure regulating valve too.
Tested the Bypass valve. Physically and electrically tested the ISV. Tested the N80.
Removed Intake manifold and reinstalled with new gasket.
Tested the Throttle Body Potentiometer too.
I can find no issues anywhere within the air intake system.
SPARK
I have verified that I do indeed get spark from each spark plug.
I have replaced the POS’s with known good 12v V6 spares and there was no change
I replaced the plugs with Bosch FR5DTC tri-electrode plugs
One possible culprit I thought could be the G40 Hall sender. I can remove it while the car is running and there is not any change in the idle.
I have read that there is no need for the G40 once the ECU sees the initial signal and starts the car. However, I have also read that if there is no signal the ECU will retard the timing. Are there two kinds of signals that the G40 sends? One for the starting of the car and another for use during driving?
I did also check and verify that I have 5v at two of the three pins
2 of my OEM coils were replaced by the PO.
If this were a miss on one of the cylinders would it act the way I am describing? Can low vacuum be a result of a misfire?
I have tried to pull injectors one at a time to identify any misfire but each injector seems to effect the running of the engine.
The exhaust pipe does seem to have a rhythmic pulsing at idle. Perhaps like there is a gap in the firing order – but I can’t say for sure.
GAS –
I have verified that each injector has voltage, I have used the self-test procedure to make each injector click.
I have not tested fuel flow or anything. I can’t think of a reason that it should have been affected.
Could I have somehow installed the injectors incorrectly?
IGNITION TIMING
This is what the issue seems like to me. The car starts at 18 psi of vacuum and instantly drops.
I wonder if my backwards chip fried something?
How would I test this?
I guess the train of thought that leads me to ignition timing is this…
What would cause this vacuum issue? Could a rough idle cause the idle issue or does the rough idle cause the vacuum issue?
Does this instead indicate a timing issue either mechanical or ECU related? Since my mechanical timing has been confirmed, that leads to ECU timing right?
If that is the case, what can make the timing be off in this way?
Any help is GREATLY appreciated. I am pulling my hair out trying to figure this out.