I'm wondering if anyone can tell me what the normal vacuum reading should be at idle for the big hose and small hose the comes off behind the throttlebody on the passenger side for a vehicle with 100k miles.

I believe my book says 17-20.

 

That sounds about right. On a stock engine, usually 18-22 is normal.

 

My v10 pulls about 17 inches at idle in drive.

 

Mine is reading about 14-15 at idle. I figure -2 for altitude being at 4,000 makes it 16-17. I still think it is weak though and the truck is sluggish.

 

Check all the usual things. Clean the MAF, change the fuel filter, change the air filter too if it hasn't been done

If you can get your hands on a fuel pressure gauge, check the fuel pressures.

With the key-on, engine-off, pressure should be around 40. With key-on, engine idling, it should be around 28-30.

If you have a long enough hose for it, check what it is when you think it's sluggish. And report back

 

thanks. will do.

 

0 vacuum when doing 65. Anyone ever heard of that?

 

Where are you getting your vacuum signal from. At steady speeds you should have close to 15 or better. At WOT you should have 0. Check the PCV hose elbows for cracks and leaks. Especially where it hooks to the back of the intake.

 

I'm tied into the small line from the connector circled in pink.

 

That's strange... I T'd into the brake booster line. Nice big fat hose...

It looks like the right spot you got, just after the throttle body.

Check for leaks like Jimmy said, he's spot on

 

update.
Changed pcv valve,
sea foamed intake,
sea foamed gas tank,
tested egr valve with vac, worked normally,
sprayed MAF with electrical cleaner,
Fuel filter looks new, so i didn't change it yet.

THinking about popping out my front O2 sensors and seeing if vacuum increases.

I'm a little leary of spraying starting fluid around my engine to spot vacuum leaks. lol

I drove to town today on a fairly flat road. With cruise set at 55, I was between 0-4 vacuum.

 

I am running 32" tires. Seems like the tranny has to work really hard to keep this boat moving, almost like it is pulling a heavy trailor.

No OBD2 codes to speak of.

I noticed one of the hoses from the evap service port on the firewall goes behind the engine somewhere. THe other one is just hanging out not attached to anything. It doesn't have any vacuum going thru it.
It looks like it should attach behind the throttlebody but someone unhooked it and put a cap over the outlet.

 

Sounds like someone cut off the evaporative recovery...

Weird that you have that low vacuum...

I run 15 inches on the highway. And most other engines I've had vacuum guages on were about 14-15.

Just for grins, can you hook it into the line going to the brake booster?

 

Same 16 at idle. Goes to 0 when you rev it, then to 20ish, then back to 16.

 

That is normal. When you just rev it, the vacuum drops. The farther open that the throttlebody is, the less manifold vacuum that you will read.
You could possibly have a converter trying to clog up. Most exhaust shops will check them for free.