odd random jerking while driving

[VX.hatch]

I've done a lots of searching and fixing but still have the same problem. The car starts up fine runs great. It's a dohc zc tuning of a chipped p28 with an oem p29 map. It has intake, header and exhaust decatted ad it was cliff. It has a newer distributor that i already rebuilt once. Plugs and wires were about a year old. The o2 is also newer. I replaced the o2 a couple of times but didn't fix the issue. Under wot and idle the car runs great.
I'm also running a one wire upgraded alternator.

The problem

The car jerks like a noob driver in first gear. It does it mainly while cruising on level ground at a steady speed. It's not as noticeable in fifth gear. The engine itself is not misfiring it's like I'm getting on and off throttle. It has energy suspension inserts that are a couple months old. It also has a new clutch that is not slipping, i promise you this.

Problem 2

When i switch between between 87 and 91 the car sputters for bit until the fuel rail switches to the new fuel. Is this normal? It runs fine afterward but just want clarification in this before i throw my turbo on.

Also the car sounds like it's spitting flames between shifts. I'm thinking this is because of no cat.


I want piece of mind that's all. I don't want to blow the motor over something simple the fix.

 

[R3dline]

i sometimes jerk it while driving, i guess it is a little odd....

 

[VX.hatch]

Now that it's cold out it's worse. It's like I'm engine breaking until the engine warms up then it's back to the above.

 

[Osiris19]

Jerking could be input shaft bearing. Most noticeable at low speed

 

[VX.hatch]

It's a new transmission same problem. When it's cold the problem multiplies to having incredible throttle response. It's like engine breaking to wot when i keep a steady foot. However clutching out it's a steady rpm at the pedal position. This exact engine was in my brothers car without a problem. When we traded engines i kept his chip but out it into a different ecu as he was auto.