car starts fine runs as it should for the first 20 min then starts to play up at junctions, engine almost stalls, revs drop to zero the bounce back up to 1k just before it stalls, its never actually cut out! throttle body has been cleaned, new idol control valve new maff sensor, new plugs and lead! so what next? no codes being stored! there was a code for the maff hence replacing! code now gone and not came back but fault still remains! any ideas>? thanks ps ive been told it could be the pipercross inducton kit but its run fine before with it on?