Why won't my car start?

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I failed a smog check which said to check egr and o2 sensor. I replaced cracked exhaust manifold with new Toyota one, o2 sensor up stream, cleaned egr valve, replaced egr modulator, and Vacuum Switch Valve. Still, the Egr symbol came on and the car died on the road. It has 175,000 miles on it and oil leak. What do you suggest I do? Thank you.