Description of the issue:

When searching for Immersive Engineering stuff in JEI fps drops like nobody business.
From over 70 FPS to mid 20s.

Crashlog:

It doesn't produce crash.

Versions & Modlist

IE : 0.12-86
Forge : 14.23.5.2768
JEI : 4.13.1.255

System spec:

Lenovo y700
i7-6700hq
( Maybe common issue with JEI?
AppliedEnergistics/Applied-Energistics-2#3813 ,
caching helped with that problem)

Debug Crash would still be nice.
Also, consider running a profiler, that may give you a hint as to why this is happening.

Here goes crash report + profiler data
crash-2018-12-06_15.51.23-client.txt
profile-results-2018-12-06_15.49.42.txt

I meant an actual external profiler, not the integrated one. Something that can actually give detailed data on what is taking up memory and do method runtime profiling.

Also, is this issue reproducable with just IE and JEI?

Only JEI and IE, FPS still happened. What profiler should I use?

I use VisualVM myself, I haven't worked with other ones, so I can't speak for them.

Profiler data https://www.mediafire.com/file/xp789dx8m1jkfd4/Profiller.7z/file
Sorry, it wasn't profiler but sampler

Tested, results are, how to say it, promising. FPS is most of the time over 30, but I don't know why those quads are so slow to render

I have done some work on this, see the commits above. They reduce the amount of rendered quads on a lot of the "big" models by a factor of 7 and reduce the amount of quads rendered for each shader item from 500 something to 3 (only in the GUI).
It would be nice if you could check whether this fixes the lag (and if it doesn't, by how much it reduces the lag), there's a maven build with those commits available here.