BuildCraft version: 7.99.33
Forge version: 14.23.5.2815
Link to crash report or log: https://gist.github.com/TheDeviantCrafter/78b1a86d8d384b173ad4c2748bb23918
Singleplayer or multiplayer: Multiplayer

The modpack I'm currently working on uses Buildcraft extensively. We have a test server running, and according to Lag Goggles, Buildcraft is frequently causing performance issues.

I've found a few specific situations where Buildcraft has the biggest performance issues:

1. Redstone engines: These consistently use 100-150 microseconds per tick, even when not active or attached to a pipe.

2. Assembly tables with items inside: If an assembly table as items in the left side of the inventory, it will use up around 100 microseconds per tick. This doesn't happen if the GUI is empty.

3. Pipes with high throughput: Pipes are fine while idle, but when several items per second are going through them it quickly becomes a performance issue. A single gold pipe can use 20 microseconds per tick. Due to the nature of the mod, this can add up fast.

Got a sampler performance report or a debug log with actual numbers?

7.99.33 is not an existant version, i assume you ment 7.99.23?

Not off hand. How would I create one?

Yes, I meant 7.99.23. My mistake.

Lag Goggles
Each buildcraft pipe creates about 24 nanoseconds of lag when alot of items run through them.
Redstone Engines cause about 200 nanoseconds of lag when they are used to extract a lot of items.
I have no clue how many items are actually running through them, I'll need to test that later.

a great guide capturing a profile: https://ae-mod.info/Profiling/ , just send it here instead of to them