What makes you think it's the spark plugs causing the problem? Have you tried simple things like resetting the ecu?
Maybe crap from the bottom of the tank got sucked up and clogged the injectors?
What "cleaner" did you use and how did you use it?
If you really want to change the spark plugs then personally I wouldn't bother with iridiums, especially if you are having problems, just put some normal coppers. NGK recommends PFR5G which looks like the platinums or BKR5EIX which are iridiums, in that case you can just go for BKR5ES which are normal coppers and go for around ~$4-5 ea.
If you don't know how to gap them correctly then just take it to a mechanic and get them to sort it out
Splitfire do make spark plugs, but whoever recommended it might have been talking about the coil packs not plugs