Spark problem or fuel problem?

[bartsau]

Well it seems the wagon is well and truly jinxed at the moment. If it is not 1 thing its another...

So over the past month or 2 it has developed what feels like a little flat spot when accelerating. Sometimes when holding a constant throttle the speed drops off a little put your foot down to the floor and give it a second to clear itself out and accelerates no problems. Sometimes when it is really bad it is almost as if it is going to slow to a complete stop, then suddenly it will clear with a backfire and take off like there was never a problem...

I have tried a second set of leads to no avail (I do wish to get a decent set but am unable to find good ones at a half respectable price). If anyone can recommend some decent leads at a reasonable price please fire away as I want to change these anyway.

It has been getting much worse in the last week or 2. Today it was as if 2 leads were on the wrong way well idling then 2 minutes later would have a slight pickup in rpm of about 100-200 and idle like a dream...

Just after ideas if this could be an intake air temp sensor, TPS, MAF, Crank angle sensor, fuel regulator, injectors, or something else.

I fitted MSD coil packs to it back in April/may.
It has iridium plugs which are just on 12 months old.
Have tried 2 set of leads (standard) both with the same effect.
Also, had a walbro GS341 fuel pump fitted about 3 weeks ago. Was ok after for a week or so and then started getting a little worse...doesn't make a difference regardless of fuel level though so thinking not this.
And last was the exhaust which was fitted 2-3 weeks ago.

Just don't know where to begin with it really.and seriously over fixing something on it almost weekly...