If nothing else I've found that this combination is super sensitive to vacuum leaks. Guess what, I discovered another leak somewhere around the throttle body. Carb cleaner sprayed here makes her want to stall. But I can't seem to determine it exactly...

I want to replace the seal, and see if that does it. Otherwise, replace the TB.

If that doesn't work, I'm going back to Djet

The engine now has better chamber filling than stock. Its not more particular to a vacuum leak, its just that its producing more vacuum.

The plenum might be cracked, which is common after 4 decades of service.

Ljet won't run properly with any vacuum leaks....any at all.

Like jake said, with better vacuum, small leaks will become big leaks now.

Clamp off the large intake hoses into the plenum.
RTV gasket the intake runners to the heads...actually to the gasket, then gasket to head.

Before Al Garcia passed away he told me that he did something to the adj on the MAF that made a big difference on his 2056. I don't know LJet so I can't elaborate. There, wasn't that helpful?

I am running that setup but with the newer cam 9590

I can hear a rushing air sound when it is running, it idles low and misses bad above 2500rpm

I haven't pin pointed the leak if it is a leak yet but those are some areas to check

I Also need to check the mixture

Is there a recommended fix for the plenum leaking at the seam?

Some sort of sealant one could pour in there and roll around to fill the seam?

Or replacement...

If you can get it running, spray some carb cleaner at the plenum if the idle changes, it's leaking.

It runs well off idle, very happy with the performance. It's the cold start and idle that I'm trying to iron out.

Need to source a new gasket. ??

With that cam cold starting isn't its strong point as its too rich. Just warm it up .