I have a '97 Cobra with a 4.6 unmodified (106,000 miles). The check engine light has been on for months; the car is still running great! the Ford dealer diagnosed - IMRC failure and "ports". Their quote was exhorbitant. Another mechanic found "coolant coming from the exhaust" - either manifold bad or if not, heads would have to be pressure tested, etc. Codes from Autozone are PO174 and PO171. Then the "marvelous mechanic" who diagnosed the coolant coming from the exhaust said he is not comfortable working on such a car!! What is the likely culprit? We absolutely love the car and baby it ever so much. Such drastic repairs are a little disappointing, given our gentle use. If it is the manifold failure only, what would be a fair replacement price? Thanks in advance!