I'll be purchasing a hand vacuum pump this weekend. I can't afford not to have one any longer. I want to verify some info first. A. When the engine is running, I should be able to push up on the EGR valve and have the engine stutter and run very poorly and almost die. This is common sense, because of the increase in exhuast gas in the intake charge. So if I push up on the valve and nothing happens, this means the EGR valve itself is clogged or broken, or the passages in the intake are completely clogged. Is this correct? B. An engine running without EGR will inherently run hotter because of the loss of the inert exhaust gases cooling the intake charge. However, a knock sensor will retard timing as seen fit to end detonation. Correct? If an EGR valve is clogged or stuck, is it worth the time to soak it in a bath of solvent, or buy a new one?