Random stuttering/stumbling

[GRSHOPR]

Hey guys, spring is here, and I'm prepping to start work again on the DD. First thing on the lists the stuttering/stumbling it has. It did it less in the older weather, but now that's its warming up (if you can call 50 degrees warm), its almost constant. It seems to lessen in severity when the engine warms up, but only slightly. It becomes more of a stutter and less of a stumbling and falling flat on its face. The interesting thing is, that after pressing the gas down about 1/3-1/2, it disappears completely. I noticed a correlation with this in the fuel trims, which, when its stuttering (before the 1/3-1/2 mark), the fuel trims are:

32 96 98 87
Trim Low Mid High

And after I cross that threshold with the gas, the trim will jump up to 100-120. I'm not too knowledgable about the fuel trims, and what exactly is going on, so I'm turning to you guys, the experts and experienced vets. I bought the car late last summer, and didn't have enough time to go over all the whole car and find all the little quirks and mods in it, but I do know it has a rebuilt JDM front clip motor, stock 94 TT ECU, stainless dp with a cat eliminator to a borla catback, EGR delete kit, and K&N HPIK. It's a 94 VR-4. Also, the ECS IS unplugged for a tower that will be replaced this summer as well. Thanks for he help in advance.

[Roybatty]

Start with intake leak test for notorious stumble. You can create your own testor but there are also some that are sold by vendors. Change o-ring of rear ic tube to turbo.

Revel in your time

[GRSHOPR]

Ok, boost leak tester arrived, going to do the test day after tomorrow. I noticed something that might be worth mentioning. The knock sensor hits double digits when this stuttering is going on. Am I correct in my understanding that the sensor registers pre-detonation by acoustic/vibration sensing on the engine block? Does that mean that the stumbling, if caused by a boost leak, could still register on the sensor?

[GRSHOPR]

Also, there are definite backfires, I'm guessing pre-detonations?

[GTOJOE]

Have you done the fuel pump resistor bypass? My car had a bad stumble at the same place every time. If I quickly pushed past the point it was OK. Turned out to be the resistor. At the point it switches from low voltage to high it stumbles. Ran perfect after bypass.

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[GRSHOPR]

I have no idea, honestly. I'll have to dig it out and check. I ran the boost leak tests, found a couple spots. It doesn't quite stumble anymore, but there is still a lagged delay for the turbos to kick in. I'll have to look into that next. This is a JDM motor with a US ECU. What's even more odd, is that I don't see an O2 sensor on EITHER bank, but the car is getting an input from somewhere. I can see the ECU reading it. Just no idea where it's coming from (already checked and confirmed, it's not the wideband). And the voltages on the rear bank get LOW. To the tune of 0.3V at times. Wondering what kind of wind those leaves rustling indicates.

Edit: just looked up the voltage range. Looks like the oxygen sensors should be 0-1V. The ECU is registering as high as 5..... Especially on the front bank.....

[GTOJOE]

O2 simulator?

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[GRSHOPR]

Haven't found one. Doesn't the fuel trim running at 120 indicate its always in limp mode?