My temps are good. I run the Neu 1515 1.5d/f in my E-MBX5T and temps rarely surpass 140*.
I have holes in the case and one fan. I also changed all the wires to 12ga. I don't know if that makes a difference or not.

Update;

I ran 3/4" of a pack thru non stop on the track under race conditions. About 15 minutes.
Motor 1515 1yf , geared 14/48, 4s 6000 mah polyquest cells, MM with a fan no other mods.
Timing set to 0
30% punch control (it stays cooler at 40%)
10% drag brake
Low on the start power (hope these settings helps someone out).

ESC was 135f
Motor 161f
Batts 116

The Losi 8T is an AMAZING truck. I smile every time I open the throttle.
This conversion is by far the most enjoyable one I have done. I have tried alot of different conversions but have they all end up getting to hot and you are always worried the electronics.