I have had a lot of problems with my car doing crazy stuff if you read through my old posts. Well turns out the obd2 ecu in my 2000 GS-R was fried. I replaced it with a OBD1 p72 and now it runs great other than low idle on cold start due to lacking a FITV. and this problem im making the thread about My old fried ecu wouldnt throw any codes at all except random misfire. It didnt throw a code for post cat o2 even though it wasnt there. I even unplugged the dead end plug for injectors and cranked it to check and it wouldnt throw a code which my buddies does. With the new obd1 ecu i am getting a code 14 which is IACV or ECU malfunction. I have been having issues with idle where it surges but not fast, it will slowly climb and fall. This was happening with the original ecu as well but the new one is far less drastic and seems almost normal but i know its not. Still with both ecu's i am having idle issues where it will only hold rpm in the process of warming up. Im also getting what i described in title. Hot or cold, idle or under load if i reach 1500 rpm under roughly 20% throttle it starts surging really fast like what i have seen from completely dead IACV's. Im also getting a solitary buck and rev hang on pressing clutch through every gear except 5th and at every rpm under 5k. I have read through enough forums to expect the responses so i will answer them before. Within the 3 months i have owned the car i have replaced dizzy, wires, plugs, fuel pump, fuel filter, fuel pressure regulator, injectors, primary o2, MAP, TPS, PCV, ECT, IAT, Temp sender, timing belt, tensioner, water pump, and ecu. I have checked timing within the last 3 days and its dead on both ignition and mechanical, the valves are properly adjusted, i have used the spray seafoam on the intake, and removed and cleaned the IACV. A leakdown test was between 8 and 12 on all 4. I have even gone through and tested every sensor and wire with a DVOM before installing the new ecu. Does my issue sound like a IACV or maybe something else? I cannot for the life of me figure out whats wrong and the bucking doesnt seem healthy for the clutch.