I have had a heck of a time trying to track down a possible vacuum leak .
I have a 451 with Pro systems Carb and nitrous plate,all gaskets have been changed from the intake up to through the carb. The problem i am have is when i take for a drive once i come to a stop it will start to lean to 18-19 AF
It has all new fuel system and filters. I do hear a slight whistle but only when i drive it! I cant get it to do in park or even in gear slightly giving gas.

 

Sounds like its lean all the time?

But just a question. What did you use to seal the intake to the cylinder heads?

 

Permatex Ultra Copper Maximum Temperature RTV Silicone

I have a innovation air fuel gauge,At idle it sits at 12-13 airfuel
I do not hear a leaking sound at idle or even in gear. Im wondering if the whistle is coming from my carb needing more

 

Do you have a different carb to try?

 

If its a Holley knock off and has a power valve it might not be opening.

 

I have a new Holley Dominator 950, I am going to pull my nitrous plate and see if that may be the issue.

 

All 4 Corner Jets are the same size?
and you have all 4 idle air screws turned out the same amounts?

Good Idea on removing the plate till you sort it out...

 

All corners are the same and everything was adjusted evenly.
Im going to slap a smoking gun tonight to see if i can see anything before i pull the plate.

 

Sounds good...

keep us posted..

 

UPDATE!
Well i put my smoking gun with air compressor. The smoke came out of both side of my primary throttle shafts! I ordered a o ring set to plug them.

 

That's kind of to be expected... A little is ok...But not lot a boat load?
Can you pull the carb and install a block off plate and retest it?


Car has Power Brake? Booster could be leaking? or maybe the vacuum actuators inside the car?