92 Q stumbling at high rpms

[tfabsQ45]

Hello,

just found this great forum and have already gleened much needed info. I have a 92 Q45 with 159,000 on her. New injectors and all hoses, new plugs and complete tune up done about 3,000 miles back. New radiator, water pump, alternator, AC compressor, all struts. Recently when I push on the accelerator and go into passing gear the rpms fluctuate and it dosen't reach full power. It seems to stumble as if the correct amount of fuel is not being supplied. Any ideas on where I should have my machanic start looking.

Also besides replacing timing chain guides, are there any further engine / fuel systems or components I should replace at this high mileage? I love the car and have decided last year to keep her and spend the money needed to get her safe and dependable for another several years.

Thank you

[911/Q45]

Check the fuel pump and filter.

[tfabsQ45]

I thought I would replace the fuel pump next because it has made noise for the last 3 years. Thank you for the tips. Also, what is JWT and where do find them? - I am always seeing posts about the JWT.