engine cough

I recently had a b16 installed, but this problem also occured in a way on my d16a6 too. With the b16, it happens in 2 places: 1)when I'm cruising at 3k rpm in 4th or 5th, just giving enough gas to stay at same speed and 2) when I get on it at around 5500 rpm. Now you should know that I'm getting a code 21 (vtec solenoid), so the check engine light is on. What I experience is the engine coughs once (makes the car slightly buck due to sudden deceleration) and the check engine light goes off simultaneously and comes back on 2 secs later. What could this be? I'm replacing the fuel filter this weekend just because. Any other ideas? Thanks.

anyone??:confused:

check your oil level and make sure you're using 10W30 or 40 or , 5W30 or 40