Sounds to me that its not tuned properly. change your fuel filter and plugs and gap them to .8.
You really need to get a wide band air fuel ratio meter on it and check how it is running to fix these kinda problems.
IF you wanted to try adding 4deg of timing over all and see if it changes the situation at all - check the power fc faq it should tell you how to do it in there from memory you go to settings then ign/inj then change the timing to +4 (remember that every time you turn the car off this setting gets reset back to 0)
if its heaps better then you need to really put a wide band on it and retune the whole ecu
ALSO what size are the wheels on your car? and what size were they on the old car? bigger wheels make the car feel doggy - dont forget that.
what compression ratio is the engine ?? do a compression test and tell me what the reading is.