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I have a 95 Z28 M6. It has all the supporting mods (Intake, exhaust, 918 beehive springs, 1.6 RR's, Isky Guide Plates, 10* locks and retainers, etc.) Had a custom cam ground for it a while back. The cam specs are as follows 224/230 .600/.600 108 LSA.

I had a PCMforless Tune done to get me a baseline. And able to drive it without fouling plugs. I bought Tuner CATS and the ALDL cable. A wideband (innovate motorsports). And started messing with it myself. I was logging extreme split BLM's. To date I have tried:

Plugs, Wires, Opti, Injectors (swapping them around to see if the Split follows sides), pulling the manifold and reinstalling to be sure there is no vacuum leak. I sprayed about 3 cans of starting fluid with it running to check everywhere for vacuum leaks. I lashed, then relashed, then relashed the valves again. Comp Pro Mag 1.6 RR's turned anywhere from 3/8 or a turn past zero lash to 1/8 of a turn past. Runs better it seems at 1/8 so thats what I am currently doing. Tried setting valve lash off going cylinder to clynder but I prefer setting it with it running, hot, valve cover off. Loosen til it clacks, tighten til noise goes away, and turn your preload on it.

In the end, I ended up going with an Open Loop tune, by me, running as much timing as I can without any knock count, at a fairly rich AFR (13:1) and it drives 1000 times smoother than it did before. AFR dips maybe to 12.8 or so on WOT passes. I plan to scale the fuel up and down 2% and see where I make the most power under WOT.

But it is very frustrating having a relatively small "street" cam that I can't run a Closed Loop tune on. I had several people mention to me in the past that it may be unavoidable with that tight of a LSA.

At the time, my cam was very similar to a LE 1.5. Just a little tighter LSA and more lift. I've ran it this way for a while. And if you pull the plugs they look fine. So why is the PCM unable to run an Open Loop Tune?

Anything else I could be missing that causes split BLM's?
 

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We know you have split blm's, but what are the readings? How big of a split? Be advised that PCM only can compensate for a very small difference. And blm of 128 on one side & 138 on the other, isn't that much of a difference.

Your engine might just be unable to have blm the same on both sides. However, I would contact pcm for less as they know more than I do.

I once had a stock engine, that would not idle below 1500 rpm. It didn't matter what I changed or did to engine, it would never idle below 1500. I learned to live with it.
 
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