when you say tweak the pump and bump boost, how would i do thiese? also it's top end speed i am after for when i drive back to UK i need to be able to sit at 70mph all day long whereas at the moment it will only do that downhill with a prevailing wind, was thinking of fitting a discovery transfer box when i come back in April, will this help with top end? at the mo it has 235/85 x 16 tyres, is it worth looking at bigger?