For those of you who are unsure of what they are, here is some bed time reading:
http://www.e30zone.net/e30zonewiki/inde ... tle_Bodies
To break it down, a converted throttle body is is bored out from 60mm to 64mm giving a 15% larger intake area, also resulting in a better throttle response as you will having a larger cross sectional area open earlier.
The BBTB will work with no other modifications, and the engine will run fine, the AFM does not need to know you have a bigger throttle it only sees the air that passes through it. The BBTB will also complement all other engine modifications, it is future proof in that respect, its fine for capacity hikes too, Alpina used one on their e30 engines.
Here is how I would like it to work. I want to convert your throttle body rather than do them on an exchange basis. This way there will be no problems giving you back a TB with more wear than the one you give me, remember these are 20+ year old parts. So you send me the throttle along with payment, I will convert it, then send you it back ready to be fitted. I'll be aiming for a one week turn around so no one is waiting too long with a car off the road.
Alternitively, I do have some throttles that can be bought outright, only 3 or 4 though, or source an extra one yourself and send it.
A basic conversion will be: Bored out to 64mm, new aluminuim butterfly, as OEM, reassembled and sent back recorded, £95.
I can do some extra bits like, a brass butterfly, nicer from an engineering respect, and soda blast the TB, as in the pics below. +£5 and +£10 respectively. The TB in the pics has been painted also, as the soda is too gentle to remove all the dark pitting that this TB had, I can bead blast which will remove the corrosion, but then the shaft bearings will then need to be changed.
From this:
To this:
So make a list, or PM me. I need 10 names to go ahead at this price.
Finally, an apology to those I have kept hanging on the line for this. Good things come...............
********After a little research, and making some measurements, I can also do BBTBs for the M30 engine. These will be bored out to 68mm from 64mm. I'll need 5 people to take up the M30 group buy and I'll be able to do them for the same price as the M20 ones.********
Many thanks Byron.
Any houndstooth appreciation discount? 
. Just a thought..