I had my engine my engine done about 8,000 miles ago it's a completely new engine and it ran good compression and everything. I recently ran into a problem where it would have a subrau rumble in boost when I heard that it started to do that I stopped driving it. Also, I would just be in any gear more likely to be in 3rd or 4th just regular driving and I would press the Clutch in completely and it would go down to like 300 rpms like it's gonna die. The Air/fuel ratio is also really bad at idle it would be at about 17.0. Also I have done to it a act clutch and fly wheel intake,innercool,radiator,full greddy exhaust and it was tuned in South Dakota. Another thing the subrau rumble started when I was done mudding with it and I know it was a dumb thing never again will that happen😂. Any help would be appreciated i am kinda a noob in this kind of stuff so please no Hate.

 

"Subaru rumble"? Misfiring is the noise you are referring to...

Check your plugs, might want to just replace the plugs and wires. Any chance you popped off an intercooler hose?
Sounds like your tune is off as well.

No problem mudding the car. The car was bred on the gravel rally stages after all.

 

At the back of the driver's side fender well see a plastic cover that protects the fuel filler tube. Pack that cover full of mud and pretty soon you'll need a new filler pipe. So, that's one area you need to make sure to get washed out.

 

check your plugs as suggested. Visually inspect your exhaust, wiring harness, oxygen sensors, cam timing positions, vacuum hoses (especially around the throttle body), do a boost leak test.

 

What are your afraid at idle on the wide band?

Could be a loss of fuel pressure.
Could be over boosting boost cut
Could be fuel cut.

How many pounds of boost when it breaks up?

 

bad coil