if the leaning the HSN made it start cutting out, did you back it off again to see if went back to not cutting out? I presume that is the HSN you are adjusting. I wonder if its the LSN thats out of tune?
Have you tried the pinch test to see if the LSN is in tune? As Zack describes above
Make ur engine run at idle then pinch fuel cable (engine will stall), but before it stalls it should rise rpm a bit. If it doesnt rise at all - u run too lean. If it raises hundreds of rpm - u run too rich.
Try this. Its very simple and very accurate.
The trouble with tuning is that the engine will konk out when its rich as well as if its too lean so differentiating between the 2 is the key. I reckon it can be quite hard to tell to be honest. Throw in air leaks and problematic clutch issues to name a few and it becomes a continuous learning process.
I was thinking if you have set the HSN at 2.5 turns and the LSN flush, the HSN could possibly be about right whereas the LSN could be a touch too rich? But I'd try the pinch test first. You can also do it by ear using the same theory as the pinch test. Lift the car off the ground and give the engine a quick rev to about 80% throttle and listen to how the engine settles. If the RPMs settle down immediately and the engine begins to bog and stalls, then its too rich. If the RPM stays high or remains high before eventually settling indicates that it is too lean. You want a compromise in between where you want it to settle into a steady idle before bogging down after 20-30secs.