big improvement but still lacking a wee bit power

hi all got my 300tdi disco in september had been sitting in garage for almost 5 years hardly moving after owner died and family held on to it 63k with service history and well above average condition

anyway with the help of landyzone either directly or by reading other threads I have improved the cars performance from a bit smoky spluttery car to a fairly smooth runner
however i find her lacking a wee bit of power when towing even lightish loads for example my ifor williams 10 x 5 livestock trailer empty she does tend to make a meal of it in fifth and fourth although not too bad in 4th

when I first got it changed oil and filters noticed slight improvement then on advice from yourselves blanked off egr big improvement stopped black plumes coming out and pulled better
changed lift pump again noticeable improvement more power
renewed entire exhaust with straight through front pipe dumping cat biggest improvement to date changed injectors and saw small improvement but I just think there should be more grunt

any suggestions

cheers

should have mentioned cleaned intercooler aswell and can hear turbo whistling away so presume it will be ok

try usin doozel instead of wee