If the SL8s are anything like the G36s,there have been some changes made by JG which are very dummyheaded.
-JG decided to cut costs and install Nylon bushings. In a gun pushing 400FPS OOTB with an M130 spring this is really bad for long term reliability. Replace with steel bushings or bearings. Even with a 1J spring required by our laws I'd still replace them. The gearbox is too high stress for nylon bushings.
-New proprietary hop up unit. It's terrible. To replace it you must replace the magwell which is thankfully still in Marui spec.
-Usual recommendation of re shimming, re greasing and aoe correction because JG don;t pay their QC department.
Overall should be the same JG stuff, super strong gearbox easily on G&G top tech levels with poor acm hop up.