Hi Rich,

Firstly well done on your choice of a Caterham.  I am pretty new to this as well, having only bought my 360R approx 12 months ago.

I agree with Michael get onto Blatchat Techtalk, there is a lot of great info and this discussion has popped up a lot.  

I had the 420 cams etc. added to my 360 in Feb this year, and the lumpiness is not that unusual (whether that right ot acceptable or not is another thing) until the engine was warmed up.

There are a number of points on blat chat that will point you in a certain direction or directions, but i felt that my engine couldn't breath properly until it had warmed up.  I added a KN filter (420 race version) at approx £55 and a decat pipe approx £260 and the difference was immediately noticable and the car sits at 1000 rpm cold, warm or hot.  The engine can get more air into the inlet and exhaust more via the outlet.  The added benefit is the sound both induction and exhaust seem better to me (subjective of course).

Good luck