Suzuki Club UK

Hi guys, I have a 98 Vitara 1.6 8v on single point with 90k miles on the clock and it has a very intermittent idle speed. When it does tick over correctly it does so as it should, when it doesn't, it fast idles at least 1500 up to 2000 RPM which this happens most of the time at the moment. There is no obvious reasons for this, it can go a fortnight without a problem and then misbehave. I have checked all vacuum pipes but most often once I lift the bonnet is starts to behave. Once when I it was happening I unplugged the MAP sensor and it went down to its normal idle speed, otherwise the engine performs perfectly.
I'm not sure if the MAP sensor would or could be intermittent or if it was a correct test procedure .
Hopefully someone on here can point me it the right directions.
Cheers in anticipation