Best to verify oil pressure problems with a mechanical gauge. If it is indeed too low you likely have worn engine bearings. If you do not have variable valve timing you can try a heavier oil which may help for a while. (By the way it is a very bad idea to post personal contact information such as email address on a public forum.)

Have you pulled the pan and checked the oil pickup screen and sludge in the pan?

Each component in the engine contributes to the combustion process. When these components fail, the oil may unintentionally enter the combustion chamber and get burned, resulting in a drop in the engine oil level and pressure. This is easily recognized as it often produces a blue smoke that exits through the tailpipe.

So if I am correct start with basic try changing filters because they play a key role in maintaining oil pressure. If the filter becomes clogged, it will increase the pressure and reduce the flow. A pressure relief valve on the oil filter prevents the pressure from getting too high. If it’s damaged, it won’t be able to do its job, allowing engine oil to flow more easily, reducing pressure.

And I will not be surprised since it is a chev. Since oil moves throughout the engine through the crankshaft bearing and the camshaft bearings. If the area has broadened because of worn parts, oil flows too easily reducing oil pressure. The oil pump must force oil through narrow areas under bearings and passageways. These are the areas that build pressure in the system because they control the rate of flow. The faster the engine moves, the higher the flow rate and pressure.

So here is what you can do If the oil light flickers on and off while the vehicle is stopped or at an idle, there may be a problem with the oil sensor or the pressure is too low. At the very least, the engine should have 5 PSI when not moving. If the PSI is less than 5, this will trigger the oil light and cause it to flicker off and on. If the light flickers while the vehicle is in motion, the oil levels may be too low. Check the oil level and add motor oil to the vehicle, if needed, and continue to monitor the light. If the oil was indeed low, the light should turn off. If not, it may be that the engine bearings are worn. This is an unfavorable situation as it may cause the engine oil to release oil from where it was once contained. A technician will need to inspect and repair it immediately.

1. Chnaged the oil sensor and oil pump but its getting more worse ?
2. Is the isse with oil grade ? And oil filter...should that be changed ?

1. I have Changed the oil sensor and oil pump but still oil light shows up when engine is heated or runs few kms , only at idle conditions /low rpm
2. Is there a issue with oil grade and oil filter...should that be changed ? How does oil grade nd oil filter  impact ? Or is there some wiring fault?