Last year season I used the weaker spring (3-20) that comes with Aero 13301set at 19 lbs FP. I was going lean on my WOT from what I observed on my logs. 19 lbs was key on, then it bled down. Idle was 14 lbs FP.

This season I set FP to 23.5 lbs key on and I note the idle FP is 13 lbs FP. I thought that a bit odd. I believed the spring rate is linear. If so how can vacuum pull it down to 13 from 23.5? But it did.

My first WOT pull of season showed 12.1 on WB commanded to 12.0. Pleased to see that.

 

How did your plumb your regulator in? I recall a thread with pics of a TBI install with the Aero 13301, but can't find it. Was gonna use it for reference.

 

Attached to the bracket that used to handle the AIR pump. This was day of install.

Edit: It is downstream of TBI unit. I fabbed a block off plate with gasket where the GM Reg used to sit. The Aeroquip lines attach to hard lines with compression fittings. The bracket hoolding the reg was also fabbed up/welded.