hi, my rs have started to jerk and splutter when it’s coming on boost. If I for example hold it at 2500 rpm in third gear, and then push down the throttle it feels like it is holding back and jerks and splutters like crazy and the rpm will only go to about 3000-3500 rpm while doing this, but the boost will go up to around 10 psi as normal. I have checked for leaks but can’t seem to find any.. could it be the plugs? Hope someone can help!

 

Just discovered that I have a big leak at my exhaust manifold gasket, could that be causing it all?

 

I wouldn't have thought the exhaust leak was the cause, but that needs sorting before anything else is done.
My car is absolutely standard. Once I was persuaded to replace the wastegate actuator. The replacement had a stronger spring and it gave symptoms similar to yours. Refitting the original removed the problem. It could still get a bit jittery on very cold damp days on the somerset levels (sea level) so I lenthened the actuator rod a turn to cure it. Previously, it had been showing 147bhp on a rolling road. Conclusion was that the boost pressure was getting higher than the ECU was happy with. Might be worth lengthening the actuator rod a couple of turns and see what that does. If it cures it, then it is possibly a boost pressure control issue.

 

Standard OE boost limit is 10 psi