recently I've encountered a problem my car loses power accelerating after 3-4 thousand rpm, two things out of the ordinary I have noticed is when I first start my car there's a knocking noise for 30 seconds and it goes away however my car does idle really rough. Goes from 1200 up to 2000rpms and it drops until the car warms up and it to goes away unless I get off the highway after driving for a couple of mins it will also occur also when lightly touching the gas pedal I hear a vibrating noise that's really hard to explain, and on top of all I hear a weird rattling noise from under my car which sounds like my exhaust, I don't have any converters on my exhaust, stock headers then a Subaru resonator and straight pipe to the eBay exhaust. I've recently replaced the spark plugs/wires my intake and used a carb cleaner to clean out my vacuum hoses, and nothing has improved, my knowledge on Hondas is slight to none, so I'm thinking it could be the vtec solenoid, egr valve or map or tbs sensor that are the reason this is happening.... Any input or advice would be greatly appreciated guys

 

Could you state the year, submodel, and engine you have in your Accord.
Would be easier to point you in the right direction.