please help

[jake1*2011]

i bought a SP reventon r speedo a while back, put it in the car and hadn't used it, so i took my Durango 410 out for a spin today just to make sure its still working fine, well it did for the first 3 or 4 minutes and it started to play up on me.

the car would cut out whilst using the throttle but it would let me brake, the car stopped and then it would run by itself until i tapped the brake again. the speedo was very hot to touch so im thinking the overheat protection kicked in but the motor was warm to touch. i haven't over-geared it ( as ive learnt my lesson from that), its not under-geared either, im running a 22 tooth pinion with a 87 tooth spur and im using the fan on the speedo.

can anyone help me? please don't say its a knackered speedo as i cant afford another one! and i thought speed passion was a good make but this is the second one ive had which has played up!

thanks jake