... assuming you are talking about the turbo MR2 ...
I am using the HKS cams: 272 intake and 264 exhaust.
You could use 264s on both sides though.
I find the idle fine and the power is wonderful.
A car with higher duration cams has a lumpier idle which some might not like.
I rather like it as it sounds rather mean
Benefits of upgrading cams is more in and out of the engine which means more power.
Automobile engines are air pumps ... the more air in and out the more power you will get if you have enough fuel to make it go bang.