900 is a wiser choice especially since your not into the lawmate thing anyways. your gps is made to work with 900, like there data link, etc. do somehting more like 500mw and we need to get you a good filter if nothing else, can get you weened off that extra battery if you want at the same time for $13 with a little regulator.... $3 if you order from china.
All them wires in there is bad............. poor kloner almost had a stroke when he opened them pics up..... your symptoms aren't surprising.
i know you don't have a disco, but this is what works. you want to mimic it as much as possible,,,,,, but it takes solder, servo ends, patience and time.
see all the twisting, wires to length, wires minimized and most noticeable no plugs, sockets, power leads...... just short pieces of wire