Buzzer...again!

I know it's been talked about so many times, but my buzzer is starting to get on my nerves. It goes off after about 15 mins of driving. The same every time I take the car out. As soon as the car goes over 2500rpm the buzzer and light stop. I can just dip the clutch or just take the car over 2500rpm and every time it will stop for seconds then come back on??? I'm pretty sure it's not dodgy oil pressure, because it comes on when i'm on the throttle!
Are there different oil pressure switches for different cars??
I've recently done an oil change and it has made no difference. When I first rebuilt the engine I had no problems, it only started after about 3-4 months after
A lot of you probably know how annoying the sound is, especially when you have passengers!! Help
Thanks
Billy

had problem before was oil pressure switch faulty

If it's on UNDER 2300 rpm it's the pressure switch at the gearbox end og the engine block….
If it's on OVER 2300 rpm it's the pressure switch on top of the oil filter…..
…that's what I found on my GTI anyway….

…or it could be a dodgy wire….I had to replace a few inches on one of mine - the cable had gone brittle and was giving totally inconsistant faults - drove me madder than I am normally !!! Still got a dodgy wire in there somewhere - comes on now and then just to let me know it's still there…..