Eps light stays on and engine sounds rough , it is tiptronic and when driven gear change / kick down is very agressive the car shudders and makes a loud knock sound then bolts forward into next gear,

Very much doubt it's related, but sounds like another coil pack has died, shuddering is likely brakes!!

The warning light is telling you the computer has found a problem that is affecting engine performance and fuel mileage. A flashing light means it is something serious.
You should have someone scan the computer for trouble codes and go from there. The codes will help direct the mechanic as to what to test.

1st to second sounds like a forced shift i would check the 1-2 shift solenoid inside the transmission and make sure the speed sensors are all in good working order, clean and apply electro grease to plugs on the transmission , as for the idle problem it could be many things from sensors for the engine to a torque converter lockup solenoid need more info is the check engine light on? you said it shudders is it missing or has a surging idle ( high and low) does it die when it goes low idle or stay running

Ckeck your govenator .

I would be checking the engine mounts as the shudder is when the engine is bouncing around under load
it it has a cable operated clutch, the problem could be that as the engine is allowed to move , it is affecting the operation of the pressure plate
it may be true that the distributor may have a problem but in this case , not electrical
distributor problems are limited ,to starting, missing, irregular timing but not what you describe

Hi Seth, Check out your engine and gear box mountings! Regards John

First of all it's normal for a car to change down a gear or two when slowing down, and if it doesn't go back into gear then you will need to check the transmission fluid to see if its needs topping up.

try your drive shaft common problem for 240sx

this could be a throttle position sensor get plugged in after market parts to replace about £25

have you had any transmission services done yet? like a flush sounds like a sticking solenoid but very hard to say with out looking into it please rate -jeff