L Series Injection Mods

Hello all.
I have 2000 L Series stock Freelander and I want to extract some more power from the engine. Recently I bought some used Rover 45 set of 4 injectors, they give some more 15 to 20 bar than the Freelander originals.
I have cleaned the injectors, tested the pressure and they were OK, once fitted on the engine, the car starts well but is very slugish reving up... Once I fit the original pilot injector, the engine revs beautifuly, fitted the Rover 45 pilot injector and slugish again, plugging in OBD diagnostic, gives intermitent error on MAF, with the original injector there are no errors at all. Did anyone already experience this?

Thanks in advance.

Hello guys

So I have been busy doing some mods on my Freelander L series. 2 days a go just changed the Fuel Injection Pump (FIP), the original is going to get an 11mm piston, in the meanwhile, the Freelander is every day use car so I have mounted a Rover 220 SDI FIP on it, the FIP was rebuild by me, it was all seized up, everything cleaned, lubricated, new seals, once mounted I had to ajust all the parameters, it is on a 2º-3º idle injection advance, 6mg/stroke diesel injection quantity, and a idle that varies from 782 rpm to 805 rpm, the motor was runing beautifuly for about 60 miles, after doing 60 miles on the road, the idle is inconsistent, unscrewed the injector fuel line and the 3rd and 4th cylinder don't seem to have enough pressure... Cold start is very difficult, and when it starts theres a massive cloud of smoke that smells a lot on diesel fuel. Could I have damage anything on the FIP when setting the parameters? But only fails after doing 60 miles?... Or the pump is not in such a good condition and only reveals itself after a few miles on the road?...

Hope to get some help, don't want to damage the engine due to bad fuel release on the cylinders...

Thanks