okay about number 3 i dont understand what the guy is tryig to say but i think he wants to stifen the suspension. thats not a bad idea thats what they do on real cars for more preformance. the bad thing about his idea of compresing the springs so there harder is that u get less suspension travel =ing worse preformance over bumps. its better to buy the suspension kit from Xmods. What would be even cheaper is to take springs from a pen and adapt them to ur xmod. ( i dont own one so im not 100% sure u can do that, I plan to get one though

). number 4 is a good idea unless those are important structural pieces. I wouldn't do it unless u race and u need every little edge u need. a better engine is good and it would give u more power. But only do his mod if ur a 100% sure of ur abilities and the products u have. ( If u dont own a soldering iron it will probably be cheaper to just buy the Xmods engine). Number 6 sounds good but dont use silicone hose use metal shims ( about 1 mm each). What most RC guys do to get a perfect mesh is stick a sheet of paper inbetween the gears and then mesh them. this give a perfect mesh. For number seven again use metal shims instead of silicone hose. the ball bearings are a great mod. just dont buy the "Oficial ones" go to the local hoby shop and buy the ones u need. none of these mods seem to put ur car at any permanet risk. So go for it if u feel confident.