Rev stalling on 3000rpm

[alastabesta]

For some reason when I press the accelerator down it won't actually go above 3000rpm... but if I press it down gradually it will... it never happened before... you guys reck'n its something major? or my exhaust's got a hole somewhere? I'm getting a clutch soon so I thought might as well do it all at one go... @_@

[FLAWLES]

my gt-z done the same under boost it made a funny farting sound and the cat converter light keept on coming on it turns out that i had fauled all four of my plugs
so have a look at the simple things first