My tuned .21 GRP tunes as well as any engine I've ever run, and just as reliable - Again, I've no idea why people are struggling so much with tuning them. I've also tuned 3 individual engines, and not one of those 3 GRP's have been a pain.

As a whole the GRP is very smooth, powerful throughout the powerband but really consistent and predictable to drive with - Awesome motor.