I am using the 3.4 plugs. Originally, the swap had the Fiero plugs, but one plug broke on removal, so all were replaced.
I do not see why the plugs would matter. Of course, knowing nothing about ignition and spark, this means little.
I can take a plug for a car and use it in my lawn mower. The gap may be a bit different, but I think DIS uses the same plugs.