any movement with this? mine started missing for a split second right before hard acceleration, then pulls fine. hoping its simple. no hard codes, haven't check soft codes yet.

 

Mine was just too much timing up top. Removed a couple degrees, it was fine. After some logs, we might add a few degrees back.

I have dual pulleys, no cats, and a VAP tune.

 

Any luck with your dyno runs? My issue turned out to be my MAF sensors.

Will be installing the upper pulley some time soon alongside my Aquamist system, hoping it keeps everything in check. After porting the supercharger, I reckon I'll be done with mods. Interested to hear how you get on

 

I think I may be having this same issue, I installed my Velocity tune and crank pulley last week. The car ran great for the first two days.. but then I started to get jerky acceleration/hesitation in the higher rpm's around 6K RPM. I noticed unburnt fuel when shifting gears and a gas smell, shortly after I had an O2 sensor go bad..

I replaced that O2 sensor and spoke with Chris. He sent me a new file with less timing, I installed and it gave it a go. This time I was able to accelerate hard for two full gears before I got a flashing check engine light. Thankfully, I was right outside my neighborhood so I pulled in, turned the car off and read the codes. P0300 (mult random misfire) Cylinder 6,7 misfire and a P1315 (persistent misfire/injector switched off).

What's bizarre is when I started the car the next day for a data log, I had no CEL and the car was running fine like nothing happened.

I have OEM coils and plugs.. I wasn't aware I needed colder ones. Could that be the answer? I also plan to check the MAF tomorrow too.

Any help would be greatly appreciated!

 

You don't "need" colder plugs, but the performance of your engine can benefit from them, and they are a good idea with the boost in power. The general rule of thumb is for every 100 hp added, you drop 1 temperature range. That being said, I imagine your issue isn't directly related to the tune, though it may be exacerbated by it. Perhaps the plugs got fouled, or there's an issue with a coil. You'll need to diagnose the misfire.

 

As Stohlen mentions, you do not HAVE to have the cooler range plugs, but is a good idea to do so if you can, and also gap them down a bit with the higher pressures. Especially at the RPM range you stated, it would point you to plugs/coils. It is possible (do not know how many miles you have) that your plugs may have been nearing useful life and they cannot handle the extra stress. I put a cat-back exhaust and tune on my 997 Turbo, and it ran great for a bit, then sputtered at mid RPMS WOT...I changed the plugs and gapped them down to .021 -(.036 recommended for this Jag application I believe) and the car smoothed out and ran great from then on! Good luck....I am waiting for my Pulley/Tune and will be putting the cooler plugs in as well....then will work on the methanol to keep it cooled down and reduce heat soak.

Keep us posted!

DC