I'm currently running the Picco Red Dot .26Max engine in my T-Maxx "3.3".
So far I'm very happy with the engine, I don't know how much better it is than the original version of the .26Max, but this version seem to have lots of torque and still winds out pretty good.
I had previously beefed up most of my driveline with steel axle shafts and center shafts and I'm running the FLM aluminum diff cups. The tranny is stock (including reverse) with the "standard ratio" gear set. I have it set to shift a bit on the early side to take advantage of the torque. With just under a gallon of fuel on this engine, the tranny is holding up very well. It broke last weekend but upon inspection if failed due to a small stone getting stuck in a tooth of the output gear, no gears were stripped. I'm running the stock clutch with the shoes in the leading position and the 24t clutch bell. That gearing seems just about right and I have no complaints with the clutch. The motor would easily pull the wide ratio gear set but I can't see the point of more top end speed, it's more than the truck can handle right now.
Currently I'm running the stock header with the resonator pipe. It seems to work pretty good actually, but it's hard to tell until I get a chance to try something else. I'm thinking to try the THS pipe with a larger dia header pipe, either the THS or maybe the O.S. header. But for now it's good enough to pull 1/2 throttle wheelies so I'm not sure how much more I want. I'm running O'Donnells 30% race blend fuel. I added an extra 0.10mm head shim per Picco's instructions. I have the HPI 1/8th buggy airfilter for now. I've been running McCoy MC9 plugs which seem to work well.
I machined my own engine mount just because I wanted to. I'm currently using the EZ-Start system and it starts the motor without any trouble. I may switch to a Tiger Drive eventually. I'd like to standardize all my vehicles on Tiger Drive at some point.
Overall I'm very pleased. It holds a tune pretty well. I have had to retune a bit if the weather changes dramatically, but not much more than 1/8 turn or so. It idles much better than the TRX motor and generally runs better, it almost never stalls out. It also starts quicker. Run times seem to equal or slightly longer than with the TRX 3.3 motor which kinda surprised me.