The 3.3 hasnt changed much since it was released. Their quality control has suffered - no two liners have the same timing. I’ve seen as much as a 10 degree in timing from a complete factory built engine and a replacement piston/liner set. The conrods are the same ones from day 1. The small end is really small and thin and NOT BUSHED. This is the biggest problem. The stock rod will hold out, but that will require abandoning the Traxxas break-in method, and customizing your store bought fuel a little bit.
I built two 3.3s from spares and found two Sirio replacement conrods for the 2.5/3.3 engines on eBay. This so far has proven to be a good change in my modified 3.3. I have pictures of the rods in that thread in this forum.
Hot Traxxas 3.3 engine build.
My go-to engine replacement for a Traxxas 3.3 would be a Novarossi 2.5SC.