2 cars 2 problems

my mates got a saxo vtr n it seems to be able to pull away ok until you change gear the it flat spots n struggles to pick up quick enuff. hes changed the fuel filter spark plugs gearbox n given it a full service in 4 months while owning it but we cant find the problem any ideas? next my missus ka has a problem with the lights shell put them on when she starts up n the rear light will be out but after 5 mins of driving say home shell park up n it will be lit. ive taken the unit out n it lights all the time once you take bulb in and out but goes out at night does same thing. also got a problem with the headlight misted up but cant see any cracks that would allow damp in. help on any of these matters would be much recieved.

ur mates vtr what are the injectors like mate? it might be that the injectors dont put out the same amount of fuel so it causes some flat spots... or maybe its the throttle. ittl have nothing to do with gearing. it will be a sensor. are there any lights coming on th dash that wouldnt normally be there? and ur missus KA could be a bad earth maybe? or dodgy fuse/relay

the vtr has an airbag light on which we cant get rid of n also the service light is on but it does need 1 think it jus needs restting tho. as for the ka ill have a look at the earth but im sure ive checked the fuses. its a 57 plate so do think it will still have warrenty?

give the saxo a service and see what difference that makes with a decent injector cleaner...like forte or simular. and u could try the ka under warentee but beware if they try charging ya a tone for a new light unit!

headlamp problem easy....
id cover the lights in masking tape n keep main beam on 4 abit.... de-mists....i do with my MoTs just so they wont fail. wrks most the time. Check the wiring on the rear lights could b as shaun said a dodgey earth connection.

the 57plate shouldnt run out til at least september...if im working this out right. check the 1st date of use on ur v5. but before u take it in ask whats still covered and ask if checking the problem is chargable under warrenty. u can get stung

WTF? are you something to do with mots???