Don't adjust fuel trim. You don't need to unless you have already messed other stuff up.
This is not a DBW vehicle (drive by wire) like the newer models which means there is a mechanical wire to operate the throttle plate inside the throttle body and hence this throttle body has an adjustable TP (throttle position) sensor in it. This TP sensor is from what the ECU knows how much wide the throttle is opened at a instance of time.
Because the pedal is not electric, hence the TP sensor lets the ECU know what position (in degrees/ volts) the throttle plate is in so ECU can adjust every other thing based on this.
As far as I remember there was one time when I needed to adjust the TP sensor when RPMs would drop when I shifted from N -> D and D -> S. Calibrated CVT using scanners and the paper clip method tons of times but could never get myself rid of RPM drops.
So one day I decided to adjust the TP sensor and I used a multi-meter, with wide open throttle it should read about 0.49V (not sure cause it's been almost 2 years before I did this. I still have got spare TBs and sensors in my tool box). But if you adjust it and it's not according to service manuals it would mess other things up e.g when you put in Drive, the ECU will now think that according to TP sensor readings and will adjust the clutches in the transmission based on that. Remember, TP sensor is what, tells your ECU how much throttle is pressed/ plate is opened.
So while on ACC mode, connect a scanner, read TP sensor values, with WOT it should read exactly at 0.49V. If it does, don't mess it up. And ya, I hate this model's IACV (idle air control valve), it sticks a lot. I used to clean it every couple of months. If by turning on AC and pressing the throttle a bit and then releasing it the RPMs drop, you gotta clean the IACV but I'd suggest you can get a good Throttle body for rs1500 very easily that has never been opened or dis-assembled before, get that, clean it and install it.
And it's just been two weeks for you since you bought this car. I'd suggest you to give it some time. I have OCD when it comes to car, but the best way is to give something time and properly test and study it.
I don't even know if your valves are adjust properly and valves gaps in IDSI and VTEC (L12A and L15A) matter a LOT!!!!!
When I adjusted the valves for the first time, there was freaking drastic improvement in economy and acceleration. Here's the link to the video I learnt from : https://www.youtube.com/watch?v=darifCUJf2A
Do follow the instructions regarding TDC and make sure to adjust to EXACT same readings as in the video or you read in this manual :
http://www.hondafitjazz.com/manual.html
This manual is for American/ Canadian Honda Fit but is great fit for our vehicles. Almost everything is identical except for a bunch of missing modules/ features.
Anyways, do give it a little bit more time. Drive it a bit more, I know you changed pumps but keep on finding better and better. This engine is more economical than I-DSI, and this is coming from someone who had both i-DSI and VTEC in his same car right? I know.
16valves (vs 8valve idsi), a baby miniature VTEC mechanism and light weight engine with 110 HP, I loved it. I regret to this day that I sold mine. I have Civic Turbo these days but I still miss this car. It was a gem. Never had gone to any mechanics for over years, I did everything on it myself. And my new cluster had fuel average on it.
I have many pictures of the car and fuel averages in my other laptop, I'll find and post them here someday.
Give it a few more weeks, drive and enjoy. Then we'll figure out what's wrong with the economy.
Thanks!
