Can the PM still issue the proposed PMI and ask for another quotation under Clause 61.1, if the quotation submitted by the Contractor under Clause 61.2 is too high for acceptance?
Does the PM still need to reply to such quotation submitted under Clause 61.2?
Yes nothing to stop that at all. If the PM considers the quote to be wrongly assessed and too high, but they have seen enough in the quote that means they want to go ahead with it, they can now instruct the Contractor to proceed with the works. They could request an additional quote pointing out why they don’t agree with the original one, or they could go on to assess it themselves and it then become implemented. This can then only officially be challenged through adjudication if the Contractor does not agree with the assessment.
NEC4 has made this process better/clearer in terms of how a proposed event becomes implemented. It also includes the requirement for the Project Manager to state the date on which the instruction to proceed will be given, making it very clear how the quote should be assessed. This is now dealt with in clauses 65.1-65.3.