S1 exhaust manifolds

[P100]

Hi guys, Im rebuilding my s1 engine, and am at the stage of looking at the exhaust manifolds. The original cast ones are looking a bit restrictive.
Are there any decent after market ones out there that anyone can reccommend ?

[P100]

Thanks for the info guys, very useful indeed !
Im now looking at the fuel injectors, which have been badly stored and I doubt will be much use. Im thinking of maybe changing to a carb set up which will be easier to maintain. I recall some while ago seeing an s2 with a holley set up. Does anyone have any info on them ?
Roy