I'm still trying to find out if the 58mm BBK Throttle Body has this passge between the IAC and the plenum as shown in this pic
http://members.***.net/chipsbyal/pag...ndex.html#rear

I called Jegs Tech line and they were of no help, I called BBK Support and have not gotten a return call and I have emailed them as well, nothing.. Went to the local speedshop, they had none in stock to look at...so....

Please let me know if yours has it and when you bought it.
Thx

 

Ok, BBK support sent me a pic of the rear of the TB, and yes it has the passage...so I guess I'll go with the Holley and jack with it till it functions right....

 

Can I ask why you are going with the Holly? do you not want the BBK because it has these holes? does the holly have that IAC port hole? and do you expect the holly Throttle Body to be difficult to get working right?

 

Yes, I'm passing on the BBK because of the IAC passage is opened up to the main plenum. I have a BBK on loan right now, thought it was an older one because I saw a post of someone claiming their BBK did not have the passage opened to the plenum, the one I have on loan is opened to the plenum and the idle speed is all over the place, sometimes the IAC counts are 0, sometimes they are 160 so something is making the IAC not able to control idle...now, that could also be because there are 2 tiny holes already in the blades...it idles fine with the stocker on it so the bad idle is related to this BBK TB...maybe if it didn't have holes in the blades already it might be fine...
But I'd rather go with a TB that is more closely designed like the stocker with that passage sealed from the main plenum and utilize the IAC idle air passages under the manifold so that each cylinder gets an even amount of idle air.
That said, the Holley has the IAC sealed from the plenum...but I have heard many stories about the idle blades sticking open...can be fixed by repositioning the spring or by boring out the manifold side just slightly..
The holley, nor any other aftermarket TB has the small venturi hole to allow some idle air thru like the stocker does (which can be seen in those pics in the link) but it can easily be added by drilling it yourself..which would only allow air into the IAC passage, and not the main plenum like drilling holes in the blades would do.
From my other post, asking what Holley owners have had to do to their TB...most say they had no problems or just drilled the venturi hole to keep IAC counts/steps down.

Hope that explains my position on it at the current moment, I'm still gathering info, but right now it looks like the Holley gets my vote.