Frozen EGR is usually the electrical side so cleaning won't help, needs a new one. Underboost is probably because you're losing boost through the open EGR valve. Or you have a boost leak in one of the pipes or the IC, hence the black smoke.
Crank the engine, and check the tester. It should be over 100 psi. If it's lower, then you have a compression problem. If you have a busted timing belt, then you won't have compression on any cylinder. SPI's are known for dropping valve seats, so you might have compression on 3 cyls, and nothing on one. Spark:
. 264 377 204 212 431 386 493 33