High vacuum readings (26) when letting off gas on fwy eating up gas as well, problem?

[Indolent]

My friend's Supra suddenly started having higher vacuum readings, just called me while he was on the freeway and he said when he'd let off the gas the vac reading wasn't the normal 20, instead 22, then later it was 26 and he noticed his gas started to go down, we're thinking a hose or pipe, or what could it be?

[DarkPhoenix]

PCV could bad. Is it stock, what kinda work is done to it, etc?

[didderson]

It's normal for my engine to create more vacuum when I let the throttle off at a higher rpm than at idle. If this only happens to him when he's on the highway then nothing is wrong. Think about it, your engine is spinning faster at a higher speed, so more air is attempted to be sucked through the intake manifold to accomodate the still running engine while the TB is closed, thus more vacuum.

[GSXRJJordan]

Originally Posted by didderson

It's normal for my engine to create more vacuum when I let the throttle off at a higher rpm than at idle.

Actually, if the motor doesn't produce more vacuum on decel than at idle, you've got a leak that's only presenting 'at pressure' (like a crack in a hose, etc).

There's no "engine problem" I can think of that will produce extra vacuum... only problems that will produce less.

[Def]

With cams I get -24 to -25 in-Hg on decel and only about -13 to -14 in-Hg at idle. 264 Step 1 HKS cams.