So now I've installed a catback and z1 intercoolers, and I'm currently installing split downpipes. So with those mods is it safe to run 0,9mm welding tips if I run 98octane fuel? I also have a boost gauge so I can check boost level. I do believe my previous Z had boost jets installed without running any ecu mods...

its not wise to turn the boost up with out knowing that the afr is doing thats working blind

I know, but I believe the stock fueling is adequate for about 0.9 bar of boost? My previous Z was running something like that for years without any ecu tune. Stock Nissan fueling on turbomaps tend to the be a good bit on the overly rich side

Apprantly you can run 12psi on the stock ECU. My advice would be not to though. The cost of having your ECU chipped is negligible in comparison to an engine. Also why limit yourself to 12psi when you could throw 14-16psi at it and get a boat load more grrr beans.

Im sure I read somewhere that using welding tips can cause boost spikes,

that's why I didn't use them and went for an apexi boost controller instead

Hence the boost gauge, if it spikes they're out.

It's just temporary, going away Saturday on a trackday so will be having access to 98 fuel. They'll need to be removed once I get home cause I don't dare to do this on 95.

I'm saving up for nistune and ebc but I got two kids, three cars and two motorbikes so it's always a battle between who gets what upgrades :-P

An MBC would allow you to dial in the boost and gradually turn it up or down as you so wished. Mine was about £15.

15£ and it holds boost? Sounds cheap and I have blown an engine with a cheap mbc before so I'm sceptical of those. No problems with the more expensive ones like Forge and such though.

When I bought my car it had these fitted along with a Zedworld chip, (no boost controller) managed 360bhp on the Dyno IIRC