Guys the rs2000 engine i had put in is giving me loads of problems.

Idle problem is bugging me as i cant find the problem anywhere

its up and down hot or cold but until last week it only did it when cold

i have removed and cleaned the iscv but no joy

i noticed under the throttle body there is a small pipe with a bolt in the end of it?? its blocking off a air inlet,when i remove it it sucks air and the revs go up?? it looks like its home made...what is ment to be there and is this causing me any problems?

Please Please Help before i sell it