Problems but No check engine light

[antz]

2002 1.8tqm with 102k completely stock
Recently APR 1+ at 100k
Added: Forge 007 installed reverse with Yellow Spring
New R revision coil packs
New NGK BRK7E spark plugs

Problems: LEAN code once with misfires so changed Coil Pack and Spark Plugs. No Recurring CEL/code problem.

When i chipped the car. Boost was spiking at 21psi no problem. Less than a week later Boost spiked at ~15psi. Then Spike went down to ~11psi.

Changed: a check valve above airbox. Rechecked the DV connections. After i checked the DV, my spike is ~8psi.

Currently: MPG has gone down drastically around 15mpg. But weather in So CAL has been hot. Don't know if that's a factor.

QUESTION: if there is a leak from the small VAC Line on the DV, can that cause boost leak? VAC is fine on my boost gauge.

Also just got an ebay vag cable and found a code:

16684 -random multiple cylinder misfire detected
p0300 -001- upper limit exceeded - intermittent


What do you guys recommend i do? There is no CEL present. Just Boost guage showing boost lost. could be from DV area as that is the only area i touched.

Summary: NO CEL , Present boost leak, VAC is fine at -20mmhg

Thanks in advance
-anthony


also need to do a rear coolant flange, fun.

[brewmastr]

there is a 90 degree hose by the intake manifold and bulkhead that is notorious for busting open and causing boost leak with no CEL, i would check that out. its so common when you go into audi to get one they know the exact hose your talking about as soon as you say "i have a boost leak"

[antz]

there is a 90 degree hose by the intake manifold and bulkhead that is notorious for busting open and causing boost leak with no CEL, i would check that out. its so common when you go into audi to get one they know the exact hose your talking about as soon as you say "i have a boost leak"

thanks for the reply, visually there are no cracks on those pipes but only a boost leak test would show.

also, on my small vac line to the Diverter valve, the cloth-like material on the outside of the hose is chewed up...

What are the symptoms to that if there is a leak at that vac line?

[brewmastr]

thanks for the reply, visually there are no cracks on those pipes but only a boost leak test would show.

also, on my small vac line to the Diverter valve, the cloth-like material on the outside of the hose is chewed up...

What are the symptoms to that if there is a leak at that vac line?

well that is just a cloth sheeth on the line, it is a rubber line underneath it, it will create a boost leak if the line is torn open, however vacuum signal is how the DV opens, if the vac line was off the DV would always be in the closed position so i highly doubt that is the problem, really closely take a look at that hose i told you about, it fools many, looks just fine to the naked eye but as soon as you boost opens wide up and leaks like a siv, also usually when you have a boost leak that is significant like that you can hear it while driving, side tanks on intercoolers are known for splitting and causing leaks and turbo inlet hose is known for collapsing causing surging boost issues.

[dougyfresh]

Definitely do a visual over the engine. If you've never touched any vacuum lines you might have a leak somewhere. Do a boost leak check as well.