Speedo problem
 

Hi guys my speedo has been playing up I think its due to the bottom cable not the top any way I disconnected it untill I got a new one !! And the engine warning light came on and on boost it was holding back !! So I reconnected it to see if that was causing it and the light has gone of and boost is fine ,how can this effect the running of the engine ? And as my speedo hasn't been working properly for a while has it effected my performance ?

goes into limp mode when no signal detected.