New Exhaust

[Pat Conlon]

Hello Jack, where did you buy this system? Any links? <edit- nevermind, I see you're in the UK>

I had the same symptoms on my '84 when I put in my stage 1 Factory Pro kit (1/8 throttle stumble)
My '84 mods: F1R slipons, (note: no header) 5*ignition advance, K&N filter panel in oem airbox
Read this, it states the necessity of setting your float heights correctly:
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

According to Factory Pro (FP), it seems that our CV36's have a common problem of our floats set to high.
So I bought a nifty float height measuring tool from FP ($49) and set my floats lower, but still within the factory specified range. The picture below is from the Factory Pro website showing the tool (not our carbs) 


I was surprised when I measured my floats to find them set so high. The factory specified float height range is 21.3mm to 23.3mm for our FJ's. My existing float height was 21.0mm so I lowered my floats to 23.0mm and the 1/8th throttle stumble went away.

Also, with your new 4 into 1, Franks suggestion of a 144 pilot air makes sense. I would do both.

Pat

This combo was advertised as being suitable for XJR 1200 and 1300's. I contacted the vendor to ask if it suited the FJ but he said he didn't know. Well I already knew that the collector would fit my downpipes as they're the same items fitted to the XJR series, so took a chance as the price (for a new item) was too good to miss. At worst I figured on new bracketry,which wouldn't be a problem as I'm a steel fabricator. In the event I didn't have to fabricate anything - it went straight on,no messing around and looks/sounds great. The guy must be missing loads of sales by not advertising it for the FJ too...

[WIFJ1287]

Make sure you have a matched set of jets/needles in there not someones jet and someone elses
needles. That can be a real bugger if it didnt run right before the mod either you might
not be set up right. I know its been a while since you were on the road with it.
+1 on a Dynajet stage one kit. I have never run so flawless Ive had that in for 14 years
and never had a problem.