Car feels a little flat and slightly underboosting
 

Got a standard Hawkeye WRX 2007 with 26k on the clock
Over the past few months it has felt a bit flat and not accelerating as quick as normal.

1) It has had recent new spark plugs
2) Always run on 97 RON fuel (Total Excellium) for the last 12 months whilst I have had the car
2) Checked air filter it was a bit dirty but only 10 months/9k miles old
3) Idle is very slightly lumpy at tickoverr (very slight judder)

Took it up to Richard Henry's this morning for a check over /test drive:

1) No ecu faults registered
2) Car is running a little lean which may explain the idle problem with the o2 sensor having to adjust the fuel by up to 9% according to the plug-in
3) Connected a boost gauge and it was boosting up to 0.7-0.75 bar, again a bit under the normal 0.9 bar?

Got it booked in with Richard Henrys again to clean out the boost control solenoid and also check for any leaks on pipes/hoses etc.

I am sure they will get it sorted but for my information/knowledge is there anything else that could be checked or could cause underboost?

Thanks

Any ideas? :idea:

Mine started very similar then started cutting out turned out to be maf sensor after it finally showed an error code it's quite easy to clean solenoid out yourself you know with some carb cleaner just a thought might save you a few pennies didn't look what car you've got but if it's a classic connect green connecters under the dash which will test all electric relays and make boost solenoid click take off all pipes to solenoid and blast through some carb cleaner n let it run through re connect and see if it cures it also where your new plugs gapped correctly

The acceleration is smooth with no misfire so I do not think the plugs are the problem unless incorrectly gapped plugs can cause the car to underboost??

Are you sure its not jut compensating for the higher ambient temperatures? I'm looking forward to cooler mornings already!!

Can the air temp affect the boost pressure so much?

My Bu*t dynamometer says yes. Last summer when it was 28 degrees, the car felt really flat, particularly after a sit in traffic.. After a torrential downpour a few hours later, temp dropped to 18degrees and the car felt alive again.