tis a 30 lump and i seem to recall the only real difference is that the 35 rubbers have a better guide top lip to help seat the carbs on. Thats why people on here say when your 30 rubbers are hardened get the 35 ones to improve things. Remember years ago on the mk1 forum here saying to do this.

its the inner lip which controls the carb position - it bottoms on the inlet ports on the heads and the carbs bottom onto the other side of the lip - unless the 30 rubbers have a thinner inner lip i cant see them being the cause of my woes? Maybe someone out there could measure their 30 rubbers and post up their readings so i can compare please??

Here's some pics of some new rubbers,I bought these of ebay addvertised as NC30,part number 16211-MLO 720,
The dimentions are,internal carb side 35.5mm.internel head side 33mm.Width in between the lugs 20mm.

my rubbers measure - 30mm aprrox carb side , 27mm head side - what is meant by width between the lugs? where exactly is that ?

When i say width i could also mean length,and when i say between the lugs it's the shortest measurement of the length face to face.hope this helps.
It seems like the 35 rubbers are a lot smaller than the 30's,that may be the problem.

thanks for all your input so far hunter - its appreciated a lot :-) I run rvf carbs anyway , ill take a pic of the first set of inlet rubbers i used and you can see the effect the head position has had on them