Hi there
Hard to recommend,but if you are looking to get most of the NA then this will and can cost you more than go route of the turbo or supercharger,have look we are tried for several moths to run NA,we are made with basic mods around 242bhp which has been enough,but we are previously run on our EP3 turbo too and going backwards to NA has been painful experience,if you once tried turbo on EP3
I would recommend have look on few projects and have look on cost of the going with turbo or SC,which is best,both have own and both are awesome to drive,I like bit more lag due this I would go with turbo
I wouldn't add any cams or any springs or retainers or large throttle body or even RBC,we are run stock throttle body at 382bhp still on 2.25" exhaust,cams are really needed if you are looking get best of the turbo,but most of the UKDM EP3 Type R cams are great and they don't need to be replaced,regarding springs and retainers yes if you are looking break 1bar,if you will be running less than 1 bar then I would keep the stock,yes get them check there
Hope this helps and good luck
Thanks,Jura