although some of these procedures sound a little "hack" they are all in theory possible,
as for the BHP gains, on a 2.0 engine yeah, why not, in a micra.... possibly half those claims. but cooler is better, and the cooler you can get the engine the better.... thermo tech exhaust wrap is the best mod for cooler engine temps, i swear by it. made my 1.3 309 spit flames....lol
you can get oil coolers, air to air intake coolers (much like an atmospheric intercooler) heat wrap for the battery, samco style coolant hoses, paint the raidiator matt blac if it isnt allready, (shiny aluminium is rubish at heat disipation) and yeah, you can possibly stand to gain a little hp.......but at least some relyability
hope that helps