Should I use a high performance oil pump or go with the stock type? I have developed a minor leak with the high performance oil pump currently installed which puddles in the garage. My mechanic says the stock oil pump performs as well for standard street use and has fewer diaphragms to fail and cause leaks. This is a slightly modified 1.8L with 93 mm pistons. Do I have to drop the engine to do the swap out? Thanks for your thoughts on this.

If your mechanic is telling you an oil pump has diaphragms you need a new mechanic, because he hasn't got a single fuching clue how an oil pump works.
This is pretty basic grade 9 autoshop knowledge.

I agree. No diaphragms.

He seems to be getting the oil pump confused with the fuel pump.

That said, the stock pump is perfectly fine for most street use, especially with a stock motor. Unless you have external oil cooling or other add-ons, using the stock pump should cause no problems.

The function of the stock pump can be improved by matching the inlet and outlet ports of the pump to the passages in the case, as well. And by setting the clearance between the gears and the housing.

--DD

Pull the engine and stick a suby in there

A stock oil pump can only leak from the paper gasket. You should be able to take it out on the car but the access is difficult.
Look at my signature for the paper gasket you need.

I'm accused of being a "hard core six guy" so you have to pull that oil pump and install a /6.

What pump do u have . What gasket prep did they use?