2001 Sable, Poor Gas Mileage

Have a 2001 Sable LS Premium, Duratec 3.0, 183,000mi.

Recently had a problem with rough morning idle and with an intermittent rough idle when stopped for lights and traffic.

Long story short, chased symptoms and occasional code and replaced EGR, IAC, DPFE, Fuel Filter, PCV, PCV Hoses, a few vacuum lines, upper and lower intake gaskets (orings), spark plugs (platinum), spark plug wires, air filter, and cleaned MAF. Probably a few other things I'm forgetting.

Car runs perfect now, idles great, no rough idle at any time any more, even 15 degree mornings when it was at it's worst before.

However, I used to get about 28-29mpg almost every tank (commute 125 miles a day all highway). I'm down to about 23-24, last tank was actually only 21mpg.

Any ideas as to why my fuel mileage might be so much lower now? Is it just the 183,000 miles catching up with the old girl?

Thanks!!!

well, last tank was back up to 27 and change per gallon, haven't changed anything. Maybe the computer was readjusting itself after being powered down multiple times over the last 3 weeks (I remove battery cable when working on engine as a habit).

Thanks.