theres nothing wrong with the radio system or the servos, the maxx is a GREAT TRUCK!!!
for the BEST hop ups and i mean the best, these are unbreakable and absolutly the best out there
http://www.unlimitedengineering.com is the place to go. its exspensive but you can replace every single part of the truck, and it will be the ultimate basher!! nothing it will stop it.
my number one recomendations for first upgrades, a venom fail safe. the UE steering linkage (to fix your steering problem. and new servos are pointless! fix the linkage first!!) and deff some nice bulk heads.
i wouldnt touch the exhaust or motor or anything for now. this truck has way more than enough power for your first truck! its a very nice truck you shouldnt have any problems with it for a long long time.
oh and the biggest piece of advice... your going to hear and see this brand called integy. their parts look cool and they have a lot of them and they are pretty cheap... and you get what you pay for. integy is the biggest waste of money ever!!! i swear stock plastic parts are better than integy lol. i bought integy arms they didnt even fit i had to modify them so they would fit, i bought integy shocks, i had ever single one bent with in 3 tanks of gas. i had steering push rods on the revo, i broke them in 5 min literally. integy is CHEAP! do not buy anything from them.
and last thing, the reason UE is the best is because they use 7075 metal for all their stuff, which is light weigh and SUPER STONG! UE stuff is unbreakable, 99% of everything else thats metal out there is 6061 which is sorta strong, but it isnt that great.