I have an os .18tm in my jato with the ez-start. Don't worry about the weight, the engine is more than powerful enough for the truck in the first place. Especially if you're not racing, the ez-start is so convenient. I would keep it if I were you, you said it yourself you had trouble with pullstarts.

Only problem with it is the header has to be grinded down about an 1/8 of an inch, maybe a little less to fit that section between the exhaust output and the ez-start. <----- I've done this it's not that hard. You can use a couple of different headers it doesn't have to be one for a tmaxx, hpi has one and there are some others out there that will work. Noone specifically makes one for the Jato yet, im not sure though.

My poor Jato is out of commission until Santa brings my Lunsford Kit. I snapped one of the stock turnbuckles last time i was out... until then my rc18t gets alot of attention