If you have them, and they're the correct ones and function correctly, put them in. 4 holes atomizer the fuel spray better, resulting in more complete mixing and combustion. This gives you the aforementioned pep and mileage increases.
I put 4 holes in and noticed the differences immediately. My build thread has the specifics of which ones I used.

 

Can you post a photo of the injectors (4-hole) you've got or just list the part number that should be stamped on the side? I've got the 703s in my '89 and while I've not seen any improvement in fuel mileage or power, the throttle response is noticeably better and they don't spew fuel all over my header the way the stockers did when they started leaking.

 

Better throttle response, smoother idle. Don't get your hopes up on the mileage.

 

Not really sure what kind but this is all I got for ya. Im thinking about swapping them back in probably this weekend after Christmas.